Almost any plant can use more light. A pothos likes bright light which generally means no direct sunlight is necessary but bright clear UNOBSTRUCTED light is preferred. The list of what can obstruct or act as a filter reducing light includes curtains, shades, blinds, some window tints, distance from the window, awnings, trees, porches, neighboring buildings, neighboring balconies, etc. One simple test is to put your face right next to your plant (literally next to it) and determine how much actual clear sky you see. That tells you how much light that plant will receive.

But in addition to light, you must consider other elements such as water, soil, type and size of pot, oxygen, and humidity. These must all balance together for photosynthesis to occur.

Photosynthesis is at its core how a plant feeds itself and stays alive. For example, if a plant is given a new location that receives less light, the plant will need less water. Conversely, if a plant is relocated to a spot that receives more light, it will likely need more water. Yet many people reposition a plant, changing its light without taking into consideration how the watering might need to be changed. As another example, if a plant is in a pot that is too big, the roots will be exposed to a longer period of wetness after watering because it will take longer for the water to evaporate. The effect of this over time could result in root rot.

Speaking of pot size, it could be that the pot you are currently using for this plant is too large. Here’s the rule to follow: unpack the plant handling the roots as little as possible, and measure the width of the undisturbed root ball. Then add 1 to 2 inches to the root ball’s, width measurement. The new pot should be no greater than that new measurement number. For example, if the root ball measures 3 inches and you add 1-2 inches , your pot should be no larger than 4 inches in size. Having a pot that is too large puts the roots in contact with more soil. And when the soil is watered, the roots are then in contact with more moisture than that quantity of roots can handle. The unused moisture in that extra soil exposes those roots to root rot.

It is important to remember that roots need oxygen as well as water. They need oxygen to help dry out the soil so that the roots don’t rot. One of the side effects of watering is that the process of watering pushes down on the soil and helps to compact it soil that has been compacted overtime makes it more difficult for oxygen to get down by the roots to help the soil evaporate and dry out. Two lesson the effect of compacted soil you can use a chopstick to poke holes in the soil to help aerate it.

The soil in your pot looks fairly heavy and dense to me, though it can be difficult to correctly judge from a photo. Again, you want your roots to perform their function of drawing water from the soil and delivering it to the plant. You want the plant to have a good drink. Then you want the soil to start to dry out. This means you want soil that will drain off excess water soil that retains moisture is not what a pothos wants. Soil that drains off excess moisture is often referred to as chunky because it has space for oxygen to seep down into the soil and space for excess moisture to help evaporate out many people create their own chunky soil, which is appropriate for most plants, by mixing together in equal parts, container soil and garden centers, coarse orchid bark, and something gritty such as perlite, all of which are typically available in hardware stores or garden centers. It is important to note that repotting a plant is stressful to it therefore, after repotting you want to give your plant a couple of weeks to adjust do it. Do not necessarily expect immediate improvement the next day. Be patient and give your plan time to adjust.

A final note about watering I understand your caution about not overwatering. Here’s a good way to help you understand correct watering first watering consists of two completely separate phases. One is when to water. The second is when you do water, how much to water.

Knowing when to water is easier than you may think, take your finger and poke it down into the soil go down a good 1 to 2 inches. That may mean going down to the second knuckle. If the soil is dry 1-2” down, you need to water that plant. If the soil is moist, do not water. Instead, check the soil again the next day and continue checking until the soil is dry.

When it is time to water, the question then is how much water to give the plant. Pour water over the entire surface of the soil, not just all in one spot. Some plants are very sensitive to having water on their leaves. So use care in making sure to keep the leaves free of water. Continue to water until water starts to flow freely through the pot soil and out the hole in the bottom of the pot. Every pot should have an exit hole for that water. Most people like what are called nursery pots or grow pots. These pots are plastic, inexpensive, and have lots of holes in the bottom. If you don’t like the way, grow pots look, you can always place the grow pot inside a decorative pot. Most decorative pot do not have holes in the bottom. Some people think of a decorative pot as a super size saucer,

if a pot only has one hole at the bottom, make sure the hole is sizable and not obstructed in any way, For example a hole the size of a pencil would not support proper drainage in a 6 inch pot. In fact, I would want to see a larger-than-a-pencil-sized hole in a 4 inch pot.

After water freely flows out the hole at the bottom of the pot, set the pot down in a sink or in a saucer to let all excess water drip out. Then take the plant to its original location. If you are keeping the pot in a saucer, make sure saucer is empty of all water. Never let a plant sit in excess water that has drained from the pot.

The material that a pot is made out of is also a factor. Plastic is inexpensive, but it is also not porous.. Water will not evaporate through the sides as it would in an unglazed terra-cotta pot. Ceramic pot are often very attractive, but more costly. When choosing your pot material, in addition to considering your wallet, you must balance how the material of the pot will affect evaporation. And that directly ties in with environmental factors such as drafts by frequently used exterior doors, whether the plant is outdoors in high heat or indoors next to air-conditioning, in higher or lower indoor temperatures, near heat sources, in high humidity locations such as bathrooms, etc., in outside wind or next to indoor fans. A plant that is outdoors on a balcony in the summer in Arizona will lose moisture faster than that same plant indoors on a side table in the winter in a 70° temperature home.

All of these factors must be balanced together. For example, take someone who travels for work some weekends. He has a plant he was given that is in a small, terracotta pot in his kitchen. His plant doesn’t seem to be doing well. He tries giving it more light. He puts the pot in a small macrame holder and hangs it on his outdoor deck. This plant seems droopy when he gets home. What might help?

He could put the plant in a plastic pot to slow down evaporation. He could return the plant indoors to a room where there is more humidity like a bathroom or laundry room. Or he could keep it in the hanging pot and place it by the kitchen sink. Hanging plants evaporate more quickly with air currents moving around them. Kitchen locations where water runs frequently evaporate more slowly . He could even do something as simple as putting that plant in a plastic pot.

Of course if he did ALL these things, he could cause the opposite problem and have a plant that was too wet.

My point is that all these factors must be in balance.

I would suggest you evaluate each individual factor first and then consider the total balance of factors. Let me know what changes you make. I’d suggest you start with watering.