Over thinking is possibly constructive and destructive.
I do it all the time.
It really is about thinking about the future at the expense of the present.
since you're going to do that anyway, keep track of all your insights during those periods.
ask yourself if the insights that you gained are worth the time you spent gaining them. then ask yourself if your time could have been better spent acting on previous insights.
then decide what serves you more.
whatever you decide be happy with it.

the world needs thinkers
the world needs doers

the 1 to do both achieves many things