Positive feedback exists. You can care about something now primarily because you've cared about it in the past. We even have a name for this: the sunk cost fallacy.

That isn't quite what the sunk cost fallacy means and one can care about something because they cared about it in the past without ever committing the sunk cost fallacy. The sunk cost fallacy requires miscalculating the expected value of a decision to pursue a particular goal due to past expenditure in seeking that goal - ie. behaving as if expenses already incurred are actually anticipated future losses for abandoning the course of action.