Keeping my mouth shut at work

I have a bad habit of speaking my mind too much at work. When somebody is sitting around on Facebook all day or blowing something important off and trying to pass it to me... I say something about it. I don’t think this is a good practice... not unless I am being backed into a corner about something should I be pointing fingers at others... I do plenty of documentation to cover myself... so I’m coming here this morning to blow off steam about this versus blasting people at work. I keep telling myself it’s not my job to tell people to get off Facebook but when those same people tell me they’re too busy to collaborate on something and do their job and they leave me completely hanging... GRRRR!