I understand what y'all guys are saying about not liking the feeling of going without, but I've actually found that wearing something on my chest increases my discomfort a lot of the time. Binding is a necessity for school, but when it's cold like this, I've found that I like to bundle up wearing nothing under. Maybe it feels good because it's closer to my natural state, or maybe the pressure around my ribs from a binder/bra serves as a continuous reminder of my chest, but either way, I've decided that going without is for me, sometimes. Especially during the monthly illness--binding is terrible during that time, as is any kind of constriction. Much better to feel free.
I've found that a lot of the time I can zone out and ignore my chest, especially if I'm not moving around a lot. That helps. Maybe some guys have difficulty blocking it out like I do. *shrug*