Antonym for "procrastinator"
I think, a synonym of "PROCRASTINATOR" is "THINKER".
Then the antonym will be DOER:
= someone who gets actively involved in something, rather than just thinking or talking about it:
// There are too many thinkers and not enough doers in this office.
(https://dictionary.cambridge.org/dictionary/english/doer)
I am a proactive person.
I am a go-getter.
These both come to mind. Go-getter may be more similar to what you have in mind.