I have learned much in the past years.
Fifteen, twenty years ago I would have been the hovering spouse, trying to be supportive, full of helpful little phrases such as "Maybe if you jiggled that little thingamajig over there, it would help get it loose," or other such ideas from a woman who has never done a plumbing job in her life but still had a better way for him to accomplish the task. And then I wasn't very happy when he wasn't very happy with me. No wonder home improvement jobs usually turned into stressful times for us all.
Now I know that the best thing I can do is just stay out of the way, preferably in another room (though available to help when he shouts out "I need you to come here a minute" to hold a tool or a light or whatever). And all he wants to hear from me is "I know you can get this done." Followed by a sincere "Thank you" when the job is done.
I've still got a lot to learn. But at least that lesson has at least had some small progress made through the years. And life is sweeter both during and after the job.