When people in interviews sometimes they ask you to describe yourself in 3 words. If you want to say that you really do what you do well, and put all your time and efforts into it, you would be a _____ person.
The kind of person you're talking about is generally called a diligent person. If you're diligent in what you do, you do it with great care and effort. For example:
He never slacks off at work because he's a diligent and hardworking guy.
Another similar word that you might find interesting would be industrious. This word is just a synonym for hardworking.
Surely, the most common term is "hard worker" (or "hard-worker") - one who is industrious and diligent in carrying out tasks or duties.
As an adjective you can use "hard-working", "diligent", "industrious", "assiduous", and "committed" all of which work in similar way.
In your example I would definitely use "diligent".