When you really look at it, most grievances are petty.
It's the emotionally immature who let anger and resentment block genuine love for someone else. These are the people who will wail with regret when there is no time left and no second chances be had.
Phillipians 2:2 then make my joy complete by being like-minded, having the same love, being one in spirit and purpose.
The way to love anything is to realize that it may be lost. ~G.K. Chesterton