You're burned out.

And why are you burned out? Because you're trying to do uni, and a business, and consulting, and a girlfriend at the same time, and you don't have the time and the brainpower to do it all.

You are finite, friend. You cannot carry this much.

So you have to pick. I do not know, but I suspect that if you're going to do the startup, you need to drop both the uni and the consulting. (Your girlfriend might have a better read on it than me; she's certainly closer to the situation than I am.)

You're clearly overworking yourself and you're burning out. Try to prioritize the things that matter the most to you, maybe a couple of things to do? I'm in high school right now, and this strategy is actually quite helpful.

I'm MUCH older than you. I definitely don't have life all figured out, but I have the benefit of many years of experience and mistakes (and a few small successes).

The MOST IMPORTANT thing that matters long term of all the things you have listed is your health.

Physical, mental, emotional.

Based on your description of things and my interpretation thereof: You are working too hard and playing too hard. And stressed that you're not working harder and playing harder. Chill, bro. Pull back. Something's got to give. If you don't choose what to pull back on, your body is going to choose for you.

I know what you mean about the last couple of things you've said. I too have had to truncate long streaks of working out because of injuries or health problems. Do what you can. You don't need to push yourself unnecessarily; just literally do what you can. If you're not "back to your old self" just yet, don't try to force it. The idea is to do better -- not to be perfect.

And for crying out loud, spend some time away from screens. Go outside (it's a cliche because it's true), take walks, look at birds, read a book for fun, maybe meditate. (Sometimes you have to focus on nothing before you can focus on anything.) If you don't have the time for it? Make the time for it. The emails businesses and the emails will wait. The girlfriend, if she's at all decent, will wait. And your schoolwork won't suffer.

One of the big follies of college is about putting an immense amount of pressure on teenagers. Putting that kind of pressure on yourself is a recipe for mishaps and mistakes. It's okay to take that pressure off of yourself. Twenty years from now you will not look back and regret not being able to do it all perfectly -- but you are at risk of regretting not focusing more on one thing and less on another thing.

And you'll definitely regret letting your health suffer if you don't take care of yourself.

If these ideas make the high-achiever part of you feel guilty or otherwise bad, consider: It's one thing if you're working hard for a particular goal and you're making a short-term sacrifice in service of that long-term payoff. But everything you're doing is so all over the place, it all seems long-term, and nothing you've said indicates that you even have a clearly defined goal. Until you have a clearly defined goal, you are subjecting yourself to noise.

Of course, you're 18. If you don't 100% know what your goals are right now, that's okay. And you're bound to err. And you're bound to make a wrong turn and have to correct. That's fine. That's normal. That's expected. Part of being 18 is figuring out your goals.

That means putting yourself in a place where you can mindfully explore and figure things out. And you can't do that well without taking good care of yourself. Take care of yourself like someone you are responsible for caring for. If you wouldn't let your son or your daughter or your pet go through a particular kind of strife, don't allow it for yourself.

Be well.