The 'You' is a kind of wild animal which is by nature extremely suspicious.
Whenever it hears a sound, it immediately becomes afraid, suspecting that there is a hunter nearby who is trying to catch it, or another animal that wants to harm it. It runs up into a tree and hides, peeking out its head and scanning all around.
After a while it climbs back down, looking here and looking there.
Only when it is sure that there is nothing around does it finally begin to relax.
But then pretty soon, it will again grow afraid, and running up into a tree, begin the same routine all over again.
Time and time again, the 'You' repeats this, with the result that it spends half of its day running up and down trees, and wastes a lot of energy.
So, when someone is very hesitant, and cannot make a decision, others often say of this person that 'the 'You' cannot decide."