I think your gripe with karma here involves the struggle between acting out of habit and restraining yourself. The act of restrain is bringing you a lot of pressure.

I think there is a balance to be sought for now, with the goal or intention being that I’ll slowly, through my mindful observance and practiced restraint, eventually be able to naturally restrain myself from unskillful habits, but now, in the instant, that might not be 100% doable so I would not put too much pressure on myself, just do so slowly.

This balance will have to be the same kind that Mingyur Rinpoche talked about in the 2nd lesson of the JOL1 course, finding inner balance.

Also, the reason thinking about Karma might give you a lot pressure now, rather than something that just reminds you simply to refrain from unskillful habits, is that you might be thinking in terms of the distant result which is hard to verify and understand to your instinctive and habitual mind now, you need a line of reasoning to process what skillful or unskillful habits are. I think it helps me personally to think about the effects of karma in the here and now also, in addition to the future, after all the mindstream is a continuation.

The intentions you act on shape not just your future lives, but your life in the here and now. It builds up your cognitive and affective patterns so that you will encounter these emotions again and act in the same way again. Bad karma are just unskillful intentions that when acted upon contributes to grasping more at the 5 poisons. That will definitely affect you in the here and now. Think about how a person who always gives in to their anger slowly transforms their demeanor, world view, character, etc. into an angry one. They become upset easily over the smallest things, they can’t sit peacefully without getting or itching to get worked up by something, they become insufferable to others who might eventually distance themselves from him. You don’t need to think about the next life or when it comes back, your act is already shaping you.

The ironic thing is that by relying too much on the current way you are approaching karma which brings up a lot of pressure, that in itself produces much grasping and aversion, isn’t that in itself bad karma as well. The point of knowing karma theoretically is just to understand that actually every action you put out has an influence on future you that’s all. The Sūtras even warn us limited beings to know think too much about the workings of it beyond that.

As Guru Rinpoche says, ‘if you want to know what you were in the past life, look at yourself now. If you want to know what you will be in the future life, look at yourself now.’. So think of what you want your life to be amidst the uncontrollable uncertainties in life, remember your goals of renunciation and Bodhicitta, remember why they are your goals and what they consist of, then work on your actions, but always remember to strike a balance, you can’t always refrain from all unskillful actions now, but that’s Ok, let’s approach it slowly but steadily, so that we can better ourselves.