Moving On and Letting Go

M.O.V.I.N.G.O.N. or L.E.T.T.I.N.G.G.O.

I wonder,
Which one is the hardest?

Can people move on but not letting go?
Or are there people who let things go but still fail to move on?

“One problem with gazing too frequently into the past is that we may turn around to find the future has run out on us.” – Michael Cibenko

Don't you think so?