What works for me is recognizing that my resentments are basically nothing more than justifications for the value judgements I place on situations. As long as I place value judgements on situations, I will find it hard to practice acceptance; and it is in acceptance that I find serenity.
Acceptance for me is not about liking or disliking, it is about recognizing a situation as being exactly as it is before I leap into value judgements.
"Why is this idiot in front of me driving 35 when the speed limit is 55 and the sun is out and there is no snow or ice on the road!!!" is non-acceptance.
"How is this person in front of me driving. They are driving slowly" is acceptance.
I can make better, more sane decisions and be more serene, if I practice acceptance. Once I have acceptance, then I can place a value judgement on the situation. Then I can decide on a course of action.
Resentments block me from acceptance. When that happens, I need to back up
and lose the value judgement and recognize a situation for being exactly as it is, warts and all.