Wanting the thing for the result of the thing is an extrinsic motivation. For example, wanting to become a doctor for the prestige, or for the pride parents would take from it.
Wanting the thing for the thing itself is intrinsic motivation. For example, wanting to become a doctor following a passion for how the body work, or helping people.
Intrinsic motivation beats extrinsic motivation everytime.
Too much extrinsic rewards for an activity that is intrinscily motivating is counter-productive.
: Researchers have found that when extrinsic motivation (such as money and prizes) are given for actions that people already find intrinsically rewarding, they will become less internally motivated to pursue those activities in the future Allison Levy et. al. / A quantitative review of overjustification effects in persons with intellectual and developmental disabilities.