Whenever I'm building something, I get really strong tunnel vision. Part of what makes me a good engineer – submerging myself extremely deep and specific context, "the zone" – seems to work against me becoming a good product person. There's always product stuff I seem to forget, or don't pay attention to, or I end up focusing on the wrong things.
After "shipping", however, the tunnel vision goes away. I can view my work with a level of clarity. Some features I built might be valuable, and some won't.
By splitting my work into build/evaluate phases, rather than continual building, I've become much better at focusing on the impact of what I'm building, and not the engineering in-and-of-itself.
I have a terrible habit of spending too much time building, and not enough time thinking/marketing/etc. This is how I try to manage that.