How bad are sins at 13? Are they not as bad as adult sins?

Im 13 and I want to lead a good life and hopefully go to heaven one day (i'm a christian). So I was wondering if sins are still counted at 13 years old, i know it seems dumb so don't flame me about it. At 13 obviously people are more prone to look at porn and think/commit lusty things with people who they are not married to, so do those people get a break in heaven? Surely there should be some cutback considering we are not fully matured in mind and how it is harder for us to control our lust?