While the temptation to hold a grudge is great, there's no time for grudges if you're thinking ahead towards positive action and endeavor.
Conflict happens. Injustice happens too. Division arises, and separation exists. None of this can stand in the way of forward movement. The challenge is to analyze the situation, cull the truth and move forward.
It's challenging to easily forgive or forget those who we perceive as our hindrances in life--the ones that distance us from our goals, pursuits and happiness. But the truth is that the longer we hold the grudge, the longer the grudge serves as an anchor to our positive direction.
Hence, there's no time for grudges. Get to the bottom of it, and move on. (Easier said than done, but a worthy goal nonetheless!)