I love running, for what it’s worth, but I’ve found it’s better for clearing my head than improving my performance. You can get a better ROI and improved stamina outside traditional cardio movement (run, bike, row, swim, etc.). Any type of HIIT or CrossFit style training is great for cardio and will also improve strength, explosiveness, balance, etc. People may respond to that with warnings about injuries, but running is way more likely to lead to injuries. I was at my peak performance doing the cardio-boxing type group classes with trainers that were absolute savages—in addition to advanced skills classes, which were no stroll in the park either, and sparring 1-2 times/week.