It's been an instructive few days, making it clear that change of this sort is not easy.
On the occasions we've made love recently, although we've started out with the best of intentions, I've managed to either overreact defensively, bringing the session to a premature end, or to change gear midway through and steer things to a not so triumphant conclusion.
Any fault is largely mine, rather than my wife's, because she is far more open to 'whatever happens', whereas I like to make what I think is 'the right' thing happen.
Specifically, I found that if we didn't 'do' enough for me to remain sexually aroused in the only way I recognise (i.e., maintaining an erection), I lost interest, to the point of not wanting to continue. A couple of times, we just rolled over and went to sleep.