I forgot the name of an adjective which means that you do something because you want to. It has a complete anytonym which sounds similar (I think they just have different prefixes) but means you do it because of outside factors. Any help is appreciated :)
The word you are looking for is intrinsic, and its antonym is extrinsic:
Intrinsic motivation involves doing something because it's personally rewarding to you. Extrinsic motivation involves doing something because you want to earn a reward or avoid punishment.
Intrinsic and Extrinsic Motivation: What's the Difference?
done, made, brought about, undertaken, etc., of one's own accord or by free choice
His joining the army was voluntary, not because he was drafted.
The opposite is "involuntary."