I'm twenty, why time pass like that

So I'm twenty years old now, kinda sad because life was easier when I was seventeen though, I think that is quite sad how much things can end and start in three years, some things wasn't so happy, ending art high school was a sad part,( I still miss my teachers) It was pretty happy time. then I lost a friend, (yes like keys in the sofa that I don't have) (it's from song if you don't know). Anyway I thought that I knew her, but In reality probably I only knew that much as she wanted to tell or show me, but she isn't the only one who was at fault, I was. I was lying to myself, and I was afraid that she would leave me, so I started to think that it would be better If I could somehow be prepared on time when we will just separate our roads. so I wasn't quite me at that time, I started to be very disappointed as a friend, I know stupid, but In the end I couldn't tell her all that what I had inside me, that worst part sad, anxious and depressed with negative thoughts - me. I really wasn't good friend in the end, and now I think that I could do this different, but in the stage of life, we don't have second chance if we really mess up. I stepped aside deliberately. So I got what I wanted and deserved in the end. Im really terrible person, I liked her and didn't wanted to hurt her, but in the end I did it. What worst on purpose, what even worse I lost her. though that's what I wanted, but in the end when she called me for last time to say goodbye, I wasn't prepared to it at all, I was so mad at me, and started to cried, for few good months, okay half a year because I didn't pass that matura exam from math, I wasn't able to go to university, and I was thinking of this so much, that I cleaned all hause, and I didn't know what to do with myself when I end doing it. When we do something that we don't want to, what we don't feel like, we end up with things that we don't want in the end and we hurt ourselves.