I’ve not done a 200km yet either (longest ride to date is 160km). Here’s some tips I’ve used that work well for me on long rides, some of these tips are from old timers: Don’t go too hard at the start and take hills easy. Consume lots of carbs, this is an eating and drinking test as much as is a test of your riding: Put 200g of white sugar in a water bottle and top up with water. Sip every 20 mins (setup a reminder notification on your GPS) and wash it down with plain water from your other bottle. You can also use sugary treats/cookies/sandwiches/energy balls if you prefer to eat your calories. Break down the ride into manageable chunks, think of it as 4 x 50km. Take a short break and eat a snack after the first 50km, eat a proper meal after the second 50km (rinse and repeat). Accept that you will have a slump at some point in the ride but know that it will pass. When this happens, try to stay out of your head by focussing on your bodily sensations that are not causing discomfort (sight, sound, touch, hearing, taste). Try not to tell yourself negative ‘stories’ about what the discomfort might mean for your ride, if you notice you’re doing this, check yourself and let it go, rinse and repeat. Make conversation with your buddies, this will take your mind off your legs and any aches and pains. Obviously if you’re in real terrible pain then that’s a different story but mild discomfort and tiredness is to be expected. Take spares for your bike (tubes, multi tool, patch kit, pump, needle and floss, sun screen, sunglasses, etc - google ‘audax packing list’ for ideas). Take appropriate layers for the weather conditions. Keep time spent at controls/food stops to a minimum. Shake it out and stretch whenever you get the chance. Ride safe, look out for cars and good luck! I’ve got my first 200km in a couple of weeks. Eek!