Thinking of another person in a romantic way is for me a clear sign that we are distracted and our relationship is not going very well.
Of course, I don’t like my partner when I’m with him look excessively other women and he doesn’t do it, I would take it as a lack of respect.
Look but without obsessions.
Then, I see other guys look at me or my partner pays the attention that they are looking at me and I feel bad for their partners.
But, as I said before, look a little is impossible to avoid but as soon as you have your partner with you, you know what it might worth and where you have to put your attention.