My basic philosophy: we're here to be good people. I pretty much don't worry about religion anymore. I believe in God and Jesus Christ solely because I find it believable, likely because of a Catholic education. But I don't conform to any religion, even Christianity (in the common sense, anyway -- I do try to follow Jesus' teachings). I figure, if being nice makes me happy, and I believe in a higher power, then there must be some reason that power put such feelings in me. Because, I don't know about you, but I feel a lot happier and even healthier to an extent when I'm being nice and helping people out. I tried it the other way through tenth grade, and it didn't work. I don't claim to have all the answers, but that's what works for me.
And yes, it involves sacrifice. That, for me, goes back to Jesus, but it's also a commonsense thing. You simply cannot win all of the time. Don't try. Give a little and you'll get back. Karma, I guess.