First, when I was around 16-17 and then off and on throughout college with the worst of it being the year and a half that spanned by grandma being diagnosed with and passing away from cancer.
I can give you a little background on both. I don't know and won't guess on what exactly you're going through, but I can share my experience in hope that it helps.
Growing up I was a pretty high achiever, with that continuing into high school. Around my sophomore year, class rank came out, I was first (hooray). No one thought I deserved to be first and made sure to tell me that. If they didn't tell me I didn't deserve it, they would tell other people. I realize this seems like a non-problem, but it really messed with my head. All of a sudden, my peers and friends were basically calling me a fraud and I was struggling not to believe them. I put an enormous amount of pressure on myself to out perform them and, when they scored a few points higher than me on the ACT, I started to crack. Around the end of the second semester, I couldn't eat, I couldn't sleep, and I was essentially having a constant panic attack. I finally told my parents, who took me to see a therapist. I was embarrassed by this, normal people weren't supposed to see therapists. I wanted to avoid medication, most of it doesn't have much of an effect on me, so we just ended up talking. 'If you don't get straight A's, what then?'; 'If you aren't number one in the class, what happens?'; a lot of these huge pressures I felt were artificial. What I took away from all of it was that instead of taking satisfaction from the progress I was making by comparing myself today to myself yesterday, I was now looking outward for validation, which is never really a good thing. It's certainly helpful to use others that are better as bar, but it is terrible to continually point out the ways you are not as good as them. By adjusting my perspective a little bit, I was able to rid myself of all of the external pressures I felt and was instead able to focus on how exactly I could be better tomorrow.
After dealing with the high school stuff, I had a pretty successful last two years of high school and ended up going to our state school to run cross country and track and to get my software engineering degree. My college career played out like this: Freshman year: broken foot, death of family friend; Sophomore year: friend accidentally shot himself; Junior year: broken foot; Senior year: grandmother diagnosed with terminal illness and passed away 7 months later, broken rib. It was not great. Honestly some of the worst and darkest years of my life. Particularly my senior year. I skipped classes for about 3 weeks both fall and spring semesters, because of what I was dealing with, just doing enough to pass my classes. It was hard. I didn't sleep. A lot of nights I wouldn't fall asleep until close to 4. I ended up taking a combination of melatonin, sleeping pills, and extra sleepy time tea just to give me a chance at sleep. Ater I broke my rib, I drank a lot more because I didn't have to worry about running. I never thought about suicide, I had seen what it could do to families and felt that whatever pain I was going through was worth it for my family and friends. I did, however, think that it might be better to just not be here anymore. I knew it wasn't realistic, but it did seem better. I was determined to deal with it on my own. I read 'The River of Doubt' (a book about one of the darkest periods of Teddy Roosevelt's life) and it helped. His methods for dealing with shit really resonated with me (basically throwing yourself into the pursuit of some grand goal) and I started feeling better.
I still have moments. Depending on the situation, different things help. One is that nothing really matters, not in like a cynical mad at the world way, more in a there is no point in not trying, because the outcome, whether success or failure, doesn't really matter. If people want to look at you differently who cares. Most of the time, you can learn and grow from your failures. Another is that emotions like 'worry' and 'embarrassment' are often pointless emotions, it's just you making yourself feel bad about something that hasn't happened yet or about what you think people are thinking about you. The stuff with my grandma still isn't easy to deal with, but I have hope that I'm still making her proud. If you're not a religious person, you can still hope that what you're doing would make them proud. The ones we love never truly leave us, it's still valid to strive for them.
Life is too awesome to give up on. And you are never as bad as you may seem. Keep your head down and your chin up. Failure is something you should be proud of, most people give up before they have the chance to fail. I know a lot of this may seem like feel good mumbo jumbo, but fuck cynicism, feel good mumbo jumbo is usually pretty spot on.
Here's a quote by a person a lot more eloquent than me:
“It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat.” - Teddy Roosevelt
A song I listened to a lot: Walt Grace's Submarine Test, January 1967 - John Mayer
If you just need someone to talk to, I would be more than happy. Just let me know your preferred method of communication, I'll reach out to you.