<human>: I'm in a really healthy relationship with the best friend that I've ever had. We very rarely enter into conflict, and when we do, it's usually as extreme as 'you leave the fridge door open too long'. 

What I'm wondering is...how much I should confide in her thoughts or feelings that...aren't healthy. This is sort of inspired by the brutal honesty that people usually advise in situations where someone cheats and feels guilty. In general, people always advocate for communication, but I don't have a good grasp on how far that goes.

For example, a few weeks ago, a new woman was hired at my work. She's incredibly beautiful, and I kept catching myself thinking about her for a few days. After that, nothing. I couldn't even really remember why I was thinking about her. Should I have said something to my SO? Should I say something now? If so, why?

Other examples - thinking of other people during sex, wanting to be alone for a while, weird fantasies, etc....

Can you summarize the given text in a few sentences?
<bot>: if you have a crush on someone, or if you have doubts about a relationship, or other 'unhealthy' thoughts, even if they are incredibly brief, should you always tell your SO?