Over my years of training and coaching martial arts I've seen many training partners and students come and go. Some students improve a lot and others don't seem to make any progress. In martial arts and particularly BJJ there is a culture of 'Just train bro' just keep turning up to class and eventually you'll get the hang of it. In my experience this is not the case, turning up to class and going through the motions is not enough to guarantee improvement and this lack of improvement will lead to loss motivation and quitting.
The key to improvement is Deliberate Practice. This is the opposite to just turning up to class and mindlessly hitting pads or doing arm-locks. It means concentrating and being focused on what you are doing with the specific intention of improving your performance.
Here are some of the basic requirements of Deliberate Practice :
A - Goals.
Having a clear 'stretch' goal of what you are working towards - Its important that this goal is something that will be quite difficult for you to achieve because this will force you grow and improve. Eg. Win all my matches by submission at my next BJJ tournament. Its also a good idea to have 'mini-goals' for each practice session Eg. Today I want to use that Combination/ Technique / Guard Pass at least 5 times in Sparring.
B - Concentration and Effort.
Full Concentration and Effort: When you are training in the gym, you are fully concentrating on what you are doing and giving it your full effort. If you are having a chat with your training partner while hitting pads don't expect to see great results.
C - Feedback.
Immediate and Informative Feedback: This could be from either a coach or from a training partner or alternatively you can just figure out how to give yourself feedback. Eg. I tried that arm-lock but my sparring partner got out of it and passed my guard - therefore what did I do wrong and what do I need to fix before next time.
D - Repetition.
Repetition with Reflection and Refinement. Lots of Repetition but not Mindless Repetition. You need repetitions with Reflection ('did I do that properly or did I screw it up?') and Refinement ('This time I'll make sure I keep my elbow close to my hip')