Everyone has something negative to say

So I know we've all probably heard "OMG get sleep now because you're not going to get any when the baby gets here, hahaha!" about a hundred times by now, but why do people have to say something negative about EVERYTHING.

I've chosen a sleep training guide that I'm going to try and implement after the first month that has a great success rate among general statistics and among people I know with multiple children. Do I think it's going to be a breeze and that it's going to work out perfectly? Of course not. Do I think it will work eventually and if I stick with it? Probably. Hopefully. But why, when people hear that do they have to say that it will never work? I literally had someone tell me today "You're deluding yourself if you think you're going to get any sleep and teach a baby to sleep through the night. You are just going to have to learn to function sleep deprived." Well OBVIOUSLY I'm going to be feeding my child every couple of hours at first, it's not like I'm going to plop him down and not feed him and expect him to sleep for 7 hours. But why do people feel the need to discourage and dismiss any attempt to try a sleep through the night routine like it could NEVER EVER work and I'm an idiot because this is my first child so better be as patronizing as possible! It's like when people say "Breastfeeding is SO hard, all you are going to want to do is quit, I bet you only make it X weeks/months." Or "Well I guess you will never get to go out/go on vacation anymore. Say goodbye to your life." Even if you think stuff like that, why in the world would you actually say it out loud?

TL;DR: I am hot and fat and currently people annoy the shit out of me.