Do not get down on yourself. The fact of life is that some people just have better genetics and are capable of training and eating poorly and still make gains (unfortunately, I am not one of them).I take a look at my training partner and some other friends of mine and they eat pizza and fried foods and drink beer and all that ****. Here I am with my tuna and protein shakes and whatnot, and they look better. Sometimes it just gets very frustrating. I feel lost, and I feel like all the work I do goes to waste, but I just don't really know how. Like I can't figure out what I'm doing so wrong, I look like someone who's never exercised in their life. Sorry for the rambling, I'm in a 'feel sorry for yourself' mood.
You need to stay positive and dedicated.