My take on this is that - yes - people tend to come back when you've "let go" - maybe not so much let go of them entirely, but decided to continue on with your life regardless, trusting that God/the universe etc will present you with the best person for you at the time, and sometimes that's nobody but yourself.
I think for a reconnect to happen - things have to change in both "energy fields". Think of it like magnets. At one point, you attracted each other. As things evolved, things went awry and there became a repulsion of some sort that one person was more sensitive to than the other (if we're truly honest, usually both people recognize some kind of tension, but one person is less inclined to hang around and stick it out/wade through it).
It could also be because we are always evolving anyway at our own speeds, and so at one point we attract each other, then one person grows but the other doesn't, or both grow but at different speeds and there's an imbalance, etc.
When the "happy place" is achieved and the magnetism is back, is when contact/a reconciliation opportunity occurs.
And most of the time if we are truly still missing/grieving them, the energy is too "heavy" for them to find an easy path back. It has to be light. So we have to process our crap and get back to happy places (whatever that means for us) to be in this area where we are able to "receive" incoming connections.
I know, sounds loopy. But that's how I think it works. It's not this stagnant, "dear psychic will we talk again?" "yes/no" it's "as things stand, yes" but that's looking at both of your energy fields. if one grows more toxic (gets more depressed by waiting, cause who ever liked waiting, for example) then it could "slow down" that chance.
But truly - I feel if we focus and go deep within ourselves, and ask ourselves is this person coming back around, we KNOW the answer. It just may not be WHEN we would like. and it might be too late. Or not.