A lot of Brazilian Jiu-Jitsu students, when they first start out, have to learn how to “turn it down” a bit. That is, they have to learn how not to go too hard against their newly found training partners; to stop being spazzy and to actually learn how to do Jiu-Jitsu. Then, as time and the belts on their waist progress, they learn how to turn up the pace properly.
However, some students haven’t been aggressive to begin with. They, up until this day, go light against their training partners (and, consequently, opponents in competition) out of fear that they’ll injure someone or be too rough on them.

This isn’t a bad quality to have, of course. But, if you have it and you want to become more successful in the Gentle Art, then you’ll simply have to learn how to better harness your aggressive side.
Nick “Chewy” Albin explains why that’s easier than you think below.

BECOME MORE AGGRESSIVE

Chewy explains that everyone – him, you, and everyone else – has an aggressive side to themselves. It’s just that it’s bottled up and shows its face in those instances when anger, frustration, and other things go through the roof inside ourselves.
Even if you’re the most non-aggressive person in the world, you still have those moments when you yell and feel like taking on the world. So, the most important thing is to recognize that there’s nothing wrong with being aggressive!

That way, and progressively, you won’t have to keep it bottled up; but you’ll start using it at the right time. Such as in training and in competition.
Chewy makes great analogies and explains excellently on the video below: