Not much to add to what's being said - I agree very much that small steps are much less painful, and also that trying to 'fix' what you see as somebody else's problem like an engineer is not a good way to approach it - that's something that I've been guilty of, and still struggle with.
It's very easy to build up resentment, particularly if it feels as though you're doing more than 50% of the work, and both Mrs. Phibes and I have been guilty of that on a number of occasions. Counselling can be quite a bit more helpful than you might imagine, but you both have to want to go.
In terms of reducing mess and clutter, we've found the Facebook Free Marketplace to be a great place for getting rid of things you don't really think you can sell, but that feel too good to just throw away - old toys, gadgets you don't need. I got rid of an old stereo which was in full working order - they guy was made up that he was getting it for free, and I was made up to free up the space. Full disclosure - our house is a lot messier than we'd like it to be.