You wish you were a better person, a better son, a better brother, and those dark urges crawl on to your brain, you try to smother yourself, you gasp, yet cannot get rid of it, throw off and be someone else!
Come to terms when you are, faced with what, why and how, mourned and regretted long enough, try something harder and start by forgiving yourself. To sit back hoping that someday, someway, someone will make things right is to go on feeding the crocodile, hoping he will eat you last - but eat you he will. So stop having pity on yourself and reclaim the life, the person you are lives in it.
You had the best of times, you went through the worst of it too, but what counts is not the mistakes you made, but you learnt not to repeat them. Free yourself and not punish. There is no shame in making the perfect choice and coming back with it even though late. Your past is what you left behind, storming in to it will wreck you and rob you of the peace you could possibly make with yourself. Look at it all a different way. Moments that were the loveliest and you wished they stay longer, things you had fun to do with and pleasures you shared will give you strength to go ahead and never feel like a half person. Follow your bliss and live on.