In an old magazine, I recently read what I thought was very good advice. It was given to the parents of a terminally ill child, but it really does apply to people who are caregivers of spouses with dementia, too.
The advice given to these parents, when they were contemplating certain end-of-life decisions, was: write down the reasons that you are making these decisions. Things seem very clear to you now, but in the future, if you start to second-guess yourself, you can go back and reread the reasons for your decision. Write down very specifically what condition your loved one is in, and why you think you are making the right decision. If you have received input from doctors or other family members, write that down, too.
I thought this was good advice for when you have to make a decision that it's time for a nursing home, or when you decide to discontinue meds, or if you ever have to make the decision to discontinue treatment.
This advice really resonated with me, because I am a champion of second-guessing. I know I will go back and think that I should have waited or made a different decision. But writing things down will make me realize that it really was the right decision that was made, and why it was the right decision.