Picture this: it is exam day at school. You turn in your paper with most questions unanswered. Your teacher asks why. Your reason? "It just wasn't right for me to answer every question." Do you really expect that to be an acceptable excuse? No! Your teacher isn't going to accept your incomplete test simply because it "was right for you." The only way that you can pass a test is to answer every question (and study).
What if you are over at your friend's house, and he leaves the room for a few minutes. While he is gone, you steal his iPod and jet back to your house. When he notices that his iPod is gone, he calls you up and asks you if you took it. "Yes, I took your iPod, but it was the right thing for me to do," you reply. Is he just going to say "Okay, man, if it was the right thing for you, that's fine." Absolutely not! There must be some universal, indiscriminate standard for what's right and what's wrong. Likewise, the only way to Heaven is to believe that Jesus is the Son of God, and to accept the free gift of salvation that He gives. Besides, who wouldn't want a gift that has already been paid for?