These are just babysteps. For example, a baby can feel frustrated, frightened, or excited by what he/she doesn't understand fully. Right now Life has all it's ups and downs in itself. And we still react the same way even when we think we understand. So the way I see it. We more youthful young adults and teens are still taking babysteps. One babystep at a time.
I really don't know, if I did my life would be a lot better. I guess just try to live in the moment and collect good memories and happy times to look back in when things gets hard
I guess all you can do is live life moment to moment; just take a lot of deep breaths to see you through; count on a few good friends to be there for you.
I guess it depends what the "bad stuff" is. Some, not saying you, may be over dramatic and how to cope is to get a better handle on reality. Or you may be depressed, and need a better outlet, so coping could be taking up something like running. Or maybe you are going through a really hard time, and coping could involve seeing a therapist to help you with your problems.
meditate for 10 minutes every morning before you start your day and for 10 minutes at the end of the evening before you go to sleep
I don't know since it could be anything, from Borderline personality disorder to bipolar... But then keep trying, have some faith in something/anything and don't lose it too often.
Only you can help yourself so be sincere to that cause.