I've been working on finding people from the 1940 census and I'll admit that I relied on memory for one thing and now I wish I had not because I was wrong. For some reason, when I was making my 1940 list, I got it in my head that my wife's great-grandfather had died and his wife had married her second husband by 1940. In doublechecking the spelling of the second husband's last name (Fluegel), I realized that husband number one died in 1941, which means I should be looking for her with him (and his last name) in 1940.
Don't rely on memory. Even when you think you're right.