Yes, one can be "too nice". "Too nice" in the sense that said "niceness/niceties" impose upon personal ambitions/plans/goals/achievement in order to accommodate another, to the point of detriment. "Too nice" can be a compromise of valuable time, emotion, capital, etc. "Too nice" could be as simple as a "yes", when "no" would have properly communicated your position, but left the other party "wanting".


I have too many examples of "too nice", so I'll just leave it at that.