Something wrong about thinking 'making up one's mind' entails taking a mind in phase state A, altering it, and arriving at phase state B. The mind itself is made-up -- the decision is reached, for instance -- via a process of continual making-up. Only by arriving at a decision can we enact the process that leads to us arriving at a decision. There's nothing prior to that telos, decision-making-wise.
A parallel case is writing: I don't decide what to write and then write it. In large part I decide what I want to want to write by writing it.