There are benefits to be gained from training at both low and high intensity, be mindful of what these are.

Always low intensity? delusion of what works, bad habits, lack of challenge. You won’t be ready for competition or real resistance.
Always Medium Intensity? Perhaps it can hinder new skill acquisition (too much pressure to try new patterns). And it still can instill false confidence.
Always high intensity? Risk of injury, no room for fine-tuning.

Mix it up.
With trusted partners.

For the sake of this map, let’s set the scale from 1 to 10.

1-5 : Low

6-8 : Medium
9-10 : High

Only training at low intensity can lead to delusion and bad habits. “No plans survive contact with the enemy”
“Everybody has a plan until they get punched in the face”
“Plans are useless, but the act of planning is invaluable”

Frameworks of Skill Acquisition (link) from other sports can be useful for BJJ too.

Don’t be afraid to communicate with your training partners if something feels wrong.

Even if your intention is a “4”, it might be perceived as a “7” by your training partner, because of different levels of knowledge, body attributes or tension. Things can also easily escalate, which is not always a bad thing, in the end we want the 緩急自在 ability.

This leads us to another crucial topic : Mismatch of Intensity.
This is where the risks of bruises and bruised egos are the highest.

Don’t crank submission.
Don’t tap too late.
Be mindful of spots in which injuries can occur.
Be the partner you wish you had.