I want to use this space to forward some health tips from Egan's profile (https://steamcommunity.com/id/pigsareit) , a TF2 mapper most well-known for the player destruction map Watergate. A few of these helped my stupid little brain survive (When it says I, that's from Egan's perspective).

1- Sleep 7+ hours a night. Sometimes it's hard but it's necessary. Otherwise you'll get a faint headache and it'll be harder to think clearly and rationally.
2- Eat enough calories based on your weight and height https://www.calculator.net/calorie-calculator.html If you aren't eating enough calories you will feel 'mentally tired all the time', and your anxiety will feel unusually much worse today 'for some reason idk why' - you are hungry, eat food. You might even crave snack foods which are high in calories.
3- Drink enough water with your food so that you can digest easier. If you feel like you get tired after meals then your stomach is either churning too hard on not enough meals per day, or you aren't sleeping enough. High saturated fat content in meals can make them harder to digest. You can counter that a bit by putting some low-fat foods (like vegetables) in your gut first.
4- Make sure your stomach is not too acidic. If it's too acidic you can feel tired from a 'mental strain'. Easy tip is to, if you sleep on your back, sleep on an incline. And if you sleep on your side, sleep on your left side so that your esophagus opens up at an angle. Helps to keep the acid low in your stomach at night. Tums can help sometimes but not after meals. You can also try taking a Gaviscon which puts a temporary foam on the top of your stomach, very useful if all else fails.
5- Caffeine can help to maintain focus, but is not a source of energy. You will need to make sure to eat enough to keep caffeine's increased-focus onto productive things. If you have caffeine on an empty stomach you can easily find yourself not eating anything for hours (unless that's your goal?).
6- Caffeine has a half life of about 5 hours, so that means if you have 2 cups of coffee, that's about 200mg of caffeine, after 10 hours you'll still have 50mg of caffeine in your blood, which is going to prevent you from sleeping easily. Here is a handy calculator to help you with intake/halflife:
https://www.gkbrk.com/wiki/caffeine-halflife/ Personally I find I need <30mg of caffeine in my blood to be able to fall asleep.
7- Caffeine also can make one anxious, I've heard that a few times. I only seem to experience this if my anxiety was bad before taking the caffeine, and then the caffeine in high doses makes it worse. At that point I'd recommend a 50 or 100 mg caffeine limit to reduce anxiety.
8- I tried for a while to only take caffeine (in pill form) on weekdays, and skip them on weekends. But the zombie-like state wasn't worth it. Now instead of going to zero on weekends I'll go down to 100 or 50 mg of caffeine, to at least be functional, while tapering down from the weekdays.
9- I do use caffeine in pill form, I get a bottle of a hundred 200-mg caffeine pills (that can snap in half to become 100mg) for $6 at walmart, they are great.
10- Caffeine also drains your body of glucose quickly to fuel its energy, so you might find you get a burst at first, and then an hour later you might crash, this is due to a lack of glucose in your blood. You can get more from whole grain healthy carbs, or otherwise from healthy fats and proteins. Also you should be aware that glutamine produced in your muscles can convert to glucose, so if you aren't exercising you might be more at-risk for this effect.
11- I speak so much about caffeine here because I found coffee flavour to be horrible, but found energy drinks at age 21 and found it helped me (with my adhd-y brain) focus on school work so much. So I've been trying to optimise how it helps without going overboard. It probably sounds like more trouble than it's worth, but I think it is worth in low doses even.
12- There's a component of green tea called L-theanine, you can buy it in supplement form. I find there's 3 effects that last 5 hours, and they stack on top of each other with more dosage: firstly is a decrease in social anxiety - useful; secondly is mild insomnia - workable; thirdly is mild sadness - wtf? Anyway I find the social anxiety reduction is sometimes worthwhile but the sadness part super sucks. I'm still experimenting with this personally.
13- Chamomile tea also can help with stress reduction. I haven't done enough personal testing to see what side effects exist. I do like that it tastes like potatoes though.