You stay true to your board. That's what makes a good draft. Guys leave as free agents and get hurt all the time....you need quality depth. The best way to infuse a franchise with talent it to draft the most talented guys.
If 2 guys are close and 1 is at a position of need, you take the need. But if 2 guys are there and 1 is head and shoulders above the other but at less of a need, you take the stud and deal with it later (unless it's a QB, you can only carry so many of those).