I'll say this as simply and succinctly as I can and it is my WORST problem too...
Some days, the bad ones, the ones where we either feel worthless, or like we have to DO things for our spouses in this sitch, we think our spouses only love us for what we've done for them lately, NOT because we are truly worthy of their love in the abstract. In this, we reduce our value to them and in turn, don't give THEM credit for being able to see past the moment and to the people we really are. It's a disservice to ourselves AND to them.
Of course, I can say that but dammit if I still don't allow that stupid way of thinking govern a lot of my life still!