Am I the only one who feels this way about past/unsuccessful deep relationships?

You're pissed off that the relationship is over, that's clear and understandable! Why shouldn't you be pissed? You let this girl completely in and then she ripped your heart out. I get it!! But you have to understand that she's not the one causing you this grief, YOU ARE! You need to truly let it go, let everything go. It's hard and it'll take time, but it's you that needs to get over it and move onto something better. You also have to realize that you're FORTUNATE! Didn't it feel great to share such moments with someone you loved and who loved you back, even though it's over now. Very few people experience that so consider yourself lucky. You gave it a shot but things didn't work out, that's life. You move on! Everything's a learning experience and in time you'll appreciate the memories for what they were.