I'm a little hungover today, so I may not make complete sense.
I think Kali is definitely right about communication being KEY. For example (storytime kiddos!).. I have major self esteem issues among a mountain of other baggage. My boyfriend knows this, and I made it clear to him what he was getting into BEFORE we started dating (we were friends for over a year before we dated).
If he makes a comment about another woman, ESPECIALLY a "normal" person walking by, I have a little freakout. Sometimes I get a little bitchy, sometimes I get a little teary- because that person seems "attainable." It's not a celebrity that he will never meet, it's someone he could bump into while getting coffee and strike up a conversation with. I trust him NOT to stray, but in my mind, I still have that voice saying "She's better than youuuuu~ He'll leave you for someone else~." He's aware that this is how I think, so he doesn't usually make comments or ogle (I think he mostly doesn't do this because he's not at a woman-buffet, he's out with his girlfriend- where he wants to be. That's just how he is).
Sometimes I talk with him about my exes, or mention something an ex and I did together, and it's usually not me just ranting about how terrible they were. My exes were a major part of my life, and a lot of my life experiences were shared with people I used to date. He generally seems ok with this. When he talks about his ex, I listen and keep my cool, but as soon as he mentions how awesome she is at something, or how much praise she got for something, I start to lose it. Generally he doesn't mention her a lot or just watches what he says because of how I feel. To anyone that isn't my boyfriend and I, this is a HUGE double standard, and I recognize this. In fact, I don't even really disagree. But the thing is, if talking about my exes bothered him, I'd stop doing it. I'm not a asswaffle. I actually pay attention to other people's feelings. I do feel bad about how one-sided things seem, and I've tried all along to get better. My boyfriend still hangs out with his ex sometimes and I grit my teeth and say I'm ok with it- because I trust him, even though my jerk-ass brain keeps telling me that it's a bad idea.
You have to know your significant other and how they will react to things (externally AND internally). Everyone is different. Be considerate of their feelings.. and you know, if you really want the relationship with them to work, you won't even see it as a chore or resent them for it. If you love them, you want them to be happy, and if that means shutting up about certain things or averting your eyes when someone attractive goes by or is on tv, then you'll do it wholeheartedly.
As a side note- the celebrity thing doesn't bother me as much. I have one fairly strong celebrity crush and a few minor ones.. I've asked my BF several times what celebrity he finds attractive, and he never can think of one. He thinks they're all too fake and bitchy, haha. If he had actually told me a celebrity he found attractive, it wouldn't upset me at all. Obviously I'd compare myself to her, but it's almost like that person isn't even real. They live in a different world. I can be jealous of them, but I'm not even on their plane of existence. It's pointless to care that much.