I absolutely hate it when my friend's happiness makes me feel so miserable
Maybe tell them how you feel? Communication is always helpful.
Yeah Shinobi's right. I can totally relate to what you feel. What happened to me was that I knew someone in school who would used to call me names and just made my life hell. But well, anything goes as kids and we were older we actually forgave each other, but some part of me didn't forgive him.
Many years later, he actually became my sister's boyfriend and I actually hated him more because I never wanted to see him again. I hated it when he came over and spent time with my sister, and there was just a lot of hatred emitting from me. Further more, he was previously an officer in the army, and now an engineering student in university. Comparing myself to him, I was nothing. I didn't do well in school, got mediocre grades in technical college, went to the army and left with a bad taste in my mouth, and searched for jobs just to earn a living. Yes, to him I was nothing. Eventually, I told him how I felt, man to man, and we forgave each other for good after this secret feud I've been secretly harboring.
If there was one thing I learnt from this, is that we shouldn't keep comparing what others are that we are not. There many things in life that people have and don't have. We know who we are and know our limitations and our abilities, and while it's good that we strive to attain what other have, you should accept the fact that this is who you are and be proud of it. Always keep thinking that I am who I am, there are things I can do which others can't. I've recently stuck by this statement, and it's been having a gradual positive impact on my way of life.
Hope this helps