Except the second half, after the… Is in the negative, si no vuele (I think maybe it should be vuelve) meaning if it doesn’t return it was never really was yours. Or, something like that.
I suppose it can be interpreted and applied in different situations but the main idea is that of ‘love’. It is meant to imply the true nature of love as being a freeing force, rather than an imprisoning force.
“Set what is yours free, if it never returns then it never was.”
Same as the english phrase “If you love someone set them free, if they never return it was never meant to be.”