We're really getting into the nuances of emotion here (which is a good thing) and I find this tool really helps:
http://feelingswheel.com (Feelings Wheel)
(I have tried to upload the image but I'm on my smartphone and it's a no go).
Resentment is a shade of anger. For me it comes from feeling burdened and overwhelmed by having to do things I don't want to do, especially when it's at the expense of what
I do want to do. This is why the trade off of doing less of what I don't want and more of what I do really helps.
It also makes it much easier to be generous with my time instead of feeling obligated. Obligation and duty are big resentment generators too.
I mean that I feel the emotion surge in my body but I seperate this from the mental chatter that comes in its wake. This is an excellent skill to develop especially if you combine it with cognitive soothing as mentioned in Alan Gordon's program.
It looks a bit like this. You walk into the room and it's strewn with stuff (toys, dogs, empty plates, whatever) and you feel your body tighten and recoil. Maybe your jaw and fists clench, or your back spasms, or your pelvic muscles boing out of place. You feel hot and bothered. And then the little voice in your heads goes...
For f**** sake. I tidied this up an hour ago. I'm sick of being a drudge. Why doesn't someone look after me for a change. I hate my f****** life. Goddam it my arse hurts. I'm sick of being in pain....
I put the brakes on after the f**** sake. I allow myself that. Then I start the soothing talk.
It's ok. Just a bit of clutter. I'll take it into the kitchen. Hmm, my jaw us a bit tense...relax baby, it's ok. Take a moment. Let's stand on the balcony and get some fresh air. Oh look, the daffodil shoots are coming through. Spring is coming! God how I love the Spring.
And I keep doing this over and over and over and after a while momentum builds and it becomes much easier.
I also throw in a few affirmations.
My home is my sanctuary.
I love the peaceful feeling of a mostly tidy house.
My home is lived in, not a show home and that feels good to me.
That kinda stuff. It is a bit fake it till you make it but how else do we learn?
Remember those toys live in magical, imaginary worlds. Let them have their lives awhile. It's sweet really.
Then you get to have that blissful time (love long baths) where you not only recharge your batteries but build energy that nourishes you and everyone around you.
This is why I go swimming twice a week. Knowing that at some point I will back in blue waters relishing some me-time serves as a great touchstone. One of my cognitive soothers is
'back at the pool in two days...think I'll have a sauna next time...wonder if that cute guy will be there..." 
Does this help?
Plum x