I can think of innumerable instances when I've felt 'Why does this happen to me?' While growing up, dating and bunch of other stuff.
I grew up in an apartment where my parents and me slept in the same room. My dad had a serious drinking problem. (He's cut down big time now) Not alcoholism. But bordering on it. And there would be days when I'd see mom get beat and cussed at for no fault of hers. So I'd go back to school on some mornings after a rough night at home thinking 'No one goes through what I go through.' (Don't get me wrong. I'm not here to pour my griefs onto you. I don't want pity.)
When I'd look around, I'd see these "happy" families going out for dinner on a Saturday night and feel sad for myself. As time passed, I scratched the surface to find everyone has their own problems. Someone had a mom who would watch crappy TV soaps all day and night and forget she had a child to take care of. Someone else didn't have a dad. And another kid whose parents were fighting over who he should live with.
Through these little experiences I realised that all of us have our own shit to deal with. The guy who cleans the cars, the lady who cooks the food, the boss at the office, the person you love and hate even... all of them have it. And it makes life a lot easier when you reach out to people, when you're kind, when you put yourself in the other person's shoes and think for that one brief moment before your about to judge someone. What would I have done if I had been the other person's place? People don't want pity or that I'm-OK-but-I-feel-sorry-for-you attitude. No. All it takes is a little understanding.
(BTW, my parents recently completed 31 years together and I love them both equally. My dad is a really great guy and my mom, words would be a waste to even try and describe what she means to me.)