I don't have all the answers, however for me it comes down to managing your training depending on your injuries, how banged up you are, what you are training for (most people it's to get better at BJJ, but also competition, fight) etc. Sometimes (could be for an extended period of time, or on a regular basis if you train 7 days/week like I do), you need to lighten up on training intensity. I do believe in training w high intensity several times/week but not every day.

1) DRILLING = perfecting positions/techniques

2) FLOW ROLLING = working with precision but focusing on stringing techniques into combinations/sequences (choose your training partners carefully, as this can frequently escalate into an all out war:) and

3) SOLO WATER TRAINING  (in addition to therapeutic effects, it incorporates elements on numbers 1 & 2 above).  If you're at the far side of the injury/banged up range, solo water training (not talking about swimming) is an excellent tool for progression. The water resistance will build speed & fluidity (you want to set up your opponent rather than go strength on strength, power on power because that's where even a less skilled but stronger opponent can prevail) but at the same time protecting you from going too far.  The buoyancy lightens up the load on your joints especially lower back, and VISUALIZATION allows you to work on your game with self-awareness of flaws in your technique that sometimes you cannot get in an intense rolling session.

are all excellent tools to help you progress without beating up your body too much.