Technically, DNA DOES influence a bit what YOU become, but environment matters way more. Imagine this: Some people could have a gene that makes it easier for them to get clinically depressed, but if they live in a safe environment, they might never get depression. Same goes for the opposite: Someone could NOT have that gene and still get clinically depressed because of the environment they live in.
Also, later I'll talk about how we transform inputs into outputs, so
I guess I'll explain that here:
If you think about it, saying that out environment influences is
just like saying that inputs from the outside world influence who we
become inside, and what we show as an output on the outside, which
could then become an input to someone else and make it so his output
has a bit of your input.
To make it simpler here's an analogy I really like: Imagine if all
your senses were stripped away, no touch, no smell, no hearing, no
taste, no sight, no nothing. Just you and your brain, without inputs
from the outside world, do you REALLY think you could form an
opinion? How would you even know what to think?