There is a bit of work in dealing with resentments. It is just one of many character defects discovered and analyzed in step four (inventory) where we learn their futility and fatality. We go on with steps five through nine to clear away the wreckage, and maintain that state with ten and eleven.
Having done the big part at age twenty two, the whole process became a lot simpler as I lived in steps 10-12, particularly step 10, cleaning up any new mistakes as I go along. This doesn't allow any new garbage to collect.
Today I find two simple prayers help me through each day. "God please take these stupid thoughts away" and "God please send me the right thought or action for this situation."
When I have had real trouble getting rid of a resentment, prayer has found the solution for me, amd that usually involves me forgiving and/or making amends for my part.
It is a design for living that really works.