no dude, you're only 18. I'm 19, one year older than you so I can vaguely imagine how much it would suck to have mitochondria disease because we've got our full lives ahead of us, it's only just beginning.
I too have thought a lot about suicide and it's on my mind a lot but one thing I've realised is that we're going to die one day anyway. So why kill myself right now if I'll die sometime in the future? I may as well just enjoy what life throws at me right now and if it gets really bad (and I'm talking really bad as in like prison or terminal illness) then suicide can be my escape plan.
But you have mitochondria disease. I'm not going to sugarcoat anything like many people here. Truth is, life is rough af. I'm not going to pretend to know what it is you're going through right now, from what I can tell it sounds harsh. I wanted to suicide as well not because of a disease but because of mental issues.
The thing is, on the internet you're going to get everyone telling you not to do it. I want to say the same thing as well but I know you've already heard it a million times. And I don't know your situation fully, if I was in your place I probably would kill myself because I'm not right in the head. But not until I've done everything I wanted to on this planet. So the least you could do is go out and experience life. Just do whatever is possible and don't give a damn about anything else.
Everyone telling you life is amazing is just saying that from their perspective because they live a lucky, happy life. But some people are not fortunate to get that. They don't understand your suffering.
Disease is one of the worst things to have, because it slowly destroys you. im sorry
The most important advice I can tell you right now is to start meditation. It's really simple, just start by doing 10 minutes everyday. I recommend going to the reddit meditation forum for a sense of community and to keep up motivation. Or find any meditation forum but I prefer the reddit one as it keeps things strictly in the realm of science only.
After you get used to it, just start by thinking to yourself "I feel better". Just repeat that for like 2 minutes during meditation. Actually say it with confidence, don't just say it. Legitimately think that you are feeling better. Also try to do it whenever you are suffering from physical or emotional pain. I guarantee you'll get results, I tried it and I've been feeling a lot better and happier than I did before. Good luck bro