Greed is described as wanting money, but in practice it is wanting this particular position to become the exceptional one. That is why it appears after the trade is already working.
The behaviours are specific: extending a target as price approaches it, adding to a winner past the planned size, refusing to trim because the move might continue. All three convert a defined-risk trade into an open-ended bet, and the give-back that follows is the standard cost. See profit-giveback.
The counter is deciding exits before entry and treating the plan as binding for that trade. If you think there is more in the move, that is an argument for a runner written into the plan, not a live amendment.
Related: profit-giveback, runner, hyperbolic-discounting, euphoria