I always have a feeling I'll end up bumping into my ex again even after having blocked him off all social media. Is it true that if it is meant to be, it will be without me doing anything?

None of us can control what another will do or what happens between us. Best not to let the lonely heart have false hope though, and plot, plan, scheme your way to a "chance" meeting. Why did you let him go in the first place? There must have been a good reason then.

Your not alone speculating on an ex, and what if though, we all do after a break up, whether it was good, bad, or in between makes little difference to our heats does it? I think that saying you quoted is about once you let go, move on with your life and live on and see what happens. Let me ask how long have you been broken up, and why?

I ask because he is still on your mind and maybe your not quite over it as you think, or having second thoughts maybe? Which is it.

No there is no truth to it. Relationships are something that has to be worked at each and everyday that you are in it. If it does not work out, most likely it was not meant to be. You do not "set someone free" they chose to go, and you have no choice but to let them go. Your issue, you have not let go, if you think they will come back at some future time.