It wasn't hard for me to pull the trigger, but I'm kind of trained in it. I've been through a divorce once and until the divorce itself, we had already gone through unfortunate things like e-mail snooping, checking phone texts, etc. During our separation, I asked my then husband that I wanted us to block each other because I didn't want him to think like "Oh, what will the wife think about? I wonder if she is watching me" each time he posted something on FB. I knew he would feel this for a while. I felt like I kind of freed my self-image and was my good old individual self. He was relieved, too. Then we didn't choose to be friends again, I think we simply didn't care.
With my BPD ex, we went through a week of him dumping me three times a day and then taking me back (we were co-habiting in my house) and I stopped reminding him that we had agreed not to dump each other each time we experienced stress. We had some CBT tools for this, but he didn't or couldn't use them. When he dumped me after attacking me physically, I said OK, this is it. I had nowhere to go (there isn't a hotel in the vicinity), ensured my safety at home and took my laptop with me - I work with it, he broke the other laptop. I immediately blocked him from FB because I knew he would be posting about us and I wasn't very strong myself after the attack and could be triggered and go and start a fight. Blocking him relieved me a lot. I think there was also a revenge feeling on my side, too, no matter how sad it is - so, you dump me and attack me, here I am blocking you on FB

Sad, I know. Still, it helped me at that time.
Now that he is gone, I sometimes crave to see what he is doing even though I never want to be with him again. I know this is about something about myself, it has nothing to do with how our relationship may turn out or how I perceive him as a partner. To me, it's just pointless curiosity, a coping mechanism for something else. I'd rather cope with the real thing and try to heal it.
Not having him on FB really helps, I find it very liberating and I think I'm doing something good for myself. I'm not proud of it but I'm proud when I realize that it's like craving and it wanes. Healing is easier this way I think. I hope it helps you, too.