Abouttoselfdestruct - it may be different for you but it certainly is that for me.
It is very complicated and I suspect very personal too. I'd count him as a close friend, he is dh's best friend, it is quite messy. I met dh and him around the same time but separately (met both through mutual friends). There was one night after I had just broken up with someone else where I considered sleeping with him but decided against it because it was too soon and then nothing romantic ever developed after that but there is a massive chemistry and our personalities compliment each other in a friendship. I never wanted him like i did want dh, I have confronted how I really feel about him I think and I think yes I'd have enjoyed a very casual fling with him but I wouldn't have ever at any stage wanted more than that with him and I knew from the first time I met dh that i did want a serious relationship with him.
It is difficult feeling attracted to someone in such a complicated situation, I think it conferred extra importance on the ordinary feelings of attraction because of the context. I tried a lot of things over it, to start I avoided him because the relationship with dh might have been threatened by the distraction at the beginning of it but he was best man at our wedding, his speech involved talking about the night I invited him in for coffee. At that point I thought he was a bit of a knob and another friend had, before I was seeing dh, warned me off him.
So there was a while when I'd actively avoid him and was pissed off but he is dh's best friend (although he lived hundreds of miles away). He would come to visit and sit and have a beer with us and started saying all this inappropriate stuff whenever dh would go out of the room "oh what if things had been different between you and I?" That kind of thing.
I told dh about it and i felt most affronted by it, although he wasn't particularly bothered himself because this inappropriateness is not unusual for this guy, but i was also affronted by the way it made me feel.
Dh and I had met, facebooked/called long distance for 6m then started seeing each other, got engaged 6m later, then he moved up here and in with me and my two children a month after that, we bought a house and moved there a month after that, we married 4 months after that and I found out days before the wedding I was pg (planned just quick). This turned out to be twins. So, things moved very quickly, there was a lot of difficulty with the twin pg (not complicated pg just difficult managing monitoring/appointments/incapacity) and his job and generally the amount of change but we were very happy. I went off sex (unusual) for 18m during pg and after birth and this incident where he was really inappropriate happened during this. When he went back home I though about it and realised it wasn't anything to do with him but the fact dh and I weren't having sex and I was angry and frustrated and that I hadn't realised I was ready but just afraid of it. It wasn't anything to do with the friend.
There were various time when he visited and there'd always be eye contact and flirting from him which I'd try to avoid and comments and little things and I'd feel ripped open inside and wracked with guilt and then he'd go away and things would be fine.
I realised after time that telling dh i was uncomfortable and trying to get dh to get him to stop with this stuff wasn't going to work and might just harm their friendship and I needed to tackle why it wasn't just something I could shrug off, which is what I would normally do.
I thought about it, I realised it is probably just that I had some stupid preconceptions about marriage that were making me feel guilty and paranoid about this situation, and obviously that he was dh's best friend, and that the reason behind it was not that this guy was a knob (as I believed) but because I felt attracted to him. Thinking about it made me able to unpick it because I had never actually believed that married people are never attracted to other people, I don't believe you can do much about the fact you will encounter people you are attracted to, what matters is how you handle that attraction as a committed person.
So I chose to tackle it head on. I thought about concepts like privacy and secrecy and what the difference is, what boundaries should be in my marriage, how I as an individual fit into it. So I made a choice that I am not going to feel bad about being attracted to anyone, that it is quite normal and that who you are attracted to (not just this guy) can be useful in determining what you are missing from your marriage and what needs working on, just like a dream is subconsciously dealing with feelings I think crushes/fixations can be your subconscious trying to show you what you are trying to deny you need not about another person you might want.
Several themes running through this for me are; freedom from domesticity/commitment, excitement, communication of feelings, sexual chemistry, shared interests, ease etc.
I have decided not to worry about some times when I become preoccupied by this guy because I am the kind of person who gets preoccupied by people and it isn't necessarily sexual, by being afraid of it and denying it it made it feel worse. So instead, because I noticed a connection between the theme of the preoccupation and something that was going on with me on my own or in my marriage, it alerted me to recognise that was what was happened and instead of feeling frustrated and fixated on this unreal thing I needed to understand why I was getting those feelings.
I confronted it with this bloke, discovered he feels the same (he is long term single but not really suited to a relationship), I've talked to my mum about it and dh although I haven't explained everything absolutely directly because I feel I'm entitled to some privacy and also because I feel I'm still sorting out some of the things in my mind.
Now, this bloke and I are quite close I'd say. I confronted it because he was moving back up here too and I knew something had to be done. Confronting it I do feel like was the right thing to do. This bloke and I both love dh and I'm not attributing more importance to it than there actually is - we have a mutual physical attraction and actually a fairly close friendship and nothing else is going on. I don't know what will happen but I think it will probably be the attraction will gradually fade (has a lot for me anyway) the more I see him as a real person and not treat him like a symbol. I'm no longer worried about it, we've been very drunk and alone and there has been no funny business. As a friend he has qualities which really add something to my life and that appears to be the way we both feel about each other. I have identified that in reality independent of dh I have never and would never want anything more to do with him intimately than as a close friend or casual relationship anyway and I'm prepared to abandon the friendship if he sees it as more than that. I also know that probably the feelings have always been more for me from him than for him from me and this is what I find attractive in a person - attraction to and interest in me so that's a bit stupid but how it is. I've learned absolutely loads about myself and my marriage and even dh through it.