~Hello!~
The enviorment can affect who we are by the way we see things after looking or witnessing something. For example, if you see something mating, of course that would probably scar you for life. I mean, it would for me. Another way enviorment can affect who we are is by how cold or hot we are. If your in a cold place, your body will try and make your body warmer quicker than a grass-hopper on the run!
Hope that helped you out!
-Hina