If you are sure that you do not wish to have children then it is a responsible decision to make. It appears from your post that you have been considering this for a period of time. If you have really considered the long term ramifications of this decision and still feel the same way, then proceed.
I see where you're coming from on this all, but still don't agree. OP was pretty clear, he meant, as did others, a xanax before hand, so as to not worry about the coming snip. There's plenty of abusive birth parents, and of course you shouldn't adopt to be a hero, but as he said, should he later change his mind there's a service that allows him to be paired with a child in need. (I personally do think some adoption services are a bit sick, with people paging through catalogues of babies like they're buying a fleece from lands' end, but meh... I mean, I'd say throw something at me, just like if it was born to me, I'll take what I get) But this doesn't mean much about the OP getting his nuts snipped. If you're adopted, your birth parents usually would have had the option to make themselves accessible at a later point, with varying degrees of cooperation with your adoptive parents, sometimes even being there like a relative the whole way. But if they didn't choose to do this, your adoptive parents ARE your parents, which is the point, and unless they're abusive (which birth parents are too, as I said) there's no reason to reject them and their love. If they're abusive, you should try to find your own way, just like you should if you have abusive birth parents. In fact, abusive adoptive parents should be much easier to rationalize and move on from than abusive birth parents, generally. OP, to me it sounds like a plan, if you feel ready, go for it(if you haven't yet). But keep in mind, as others have said, it is still possible to father a child. I used to know someone who was conceived after his dad had a vasectomy.
CRAP?! Sounds painful! If you were watching them do the procedure you would be sick - they pull the vas deferens out of your nuts URGH
For couples who are secure in not wanting to have kids or any more kids, sectional vasectomy is the most effective and least invasive procedure. Condoms can be situation invasive and female sterilization is more complicated.