Vary your intensity: Your day in Jiu jitsu was probably pretty similar to mine and everyone else reading this post – you locked up with your opponent and gave everything you had at maximum power until you quickly exhausted yourself and got finished. The path towards expertise is largely bound up with and INTENSITY. It doesn’t matter how well conditioned you are – if you go at maximum intensity for a length of time, you will get exhausted. The key is to understand that high intensity is only required for brief periods in Jiu jitsu, usually when either attacking or defending a potential score or submission. This is only a tiny fraction of the total time of any given match. The rest of the time you should be a state of relatively relaxed, but alert, calm. Learning to cycle between long stretches of calm and short of high intensity effort is a huge part of your development and is the true key to endurance on the mat. The better you get at this skill, the longer you can train and the fewer injuries you will suffer. In addition your sparring will become a lot more enjoyable as a side benefit. If you have a time playing calm, make a note to stop in certain positions where you feel you can recharge and compose yourself, then as you improve, stretch those positions out more and employ more positions. Make it your goal to spend 70-80% of a match in a fairly calm state so you can save yourself for the 5-10% where the match is won and lost.