If you want a fuck buddy to just have sex with every once in a while, you need to separate yourself from him as a person. This is the problem with fuck buddies. You need to check yourself if you have feelings for the person. Basically, treat them like a sex toy and do not care other than that.
Most of all, keep yourself open to other men. It's likely that the fuck buddy is keeping himself open to other women, so you need to be open to other men. If you can keep yourself from giving a fuck about the fuck buddy, you can keep yourself open to other men.
The issue with fuck buddies is that someone will find someone they care about (basically ending the relationship), so you don't want to be that person who cares and gets hurt. Always let yourself be open to other people, and go out with them. The very premise of fuck buddy is that they are there until you find someone better, and it's better to be the one who finds someone better than being the one who cares. Remember that.
The only issue I have with fuck buddies is that it's somewhat a grey area. If you are the one who cares, you are the one who gets hurt. If you don't give a shit, you are in control, so you want to be the one in control not necessarily of him but in your own feelings. If you are someone who has to have a connection before you have sex, then you are surely the one who gets hurt. Really the solution is to keep yourself separated and have sex when you feel like it but keep yourself open. If you meet a guy, go out with them and see where it goes! I promise you if you've been in that fuck buddy situation, it's far more satisfying than being the sucker who is on call. The very key to being a fuck buddy is not giving a shit. Take it from someone who went from GF to fuck buddy in a relationship, not giving a shit will make it a whole lot easier.
Personally, I feel there is something unattractive about someone who will be a fuck buddy and therefore it's easier to give them up. As hard as it is, you have to realize that you are being used, and you are using the other party. If you can separate yourself, then you are less likely to get hurt. That is the main issue with fuck buddies; who will get hurt. If you are someone who cares more easily, it's likely to be you, so tell yourself instantly that the guy is a POS and you don't care, and you can mitigate your damage while still having fun in the long run.