There are many similarities between combat sports and weight training.
In both sports, your weaknesses aren’t revealed until you’re truly tested. You don’t know how weak your hamstrings are until you fold over during a max squat. You don’t know how shitty your cardiovascular endurance is until your opponent pushes you at a pace that makes you quit.
Whether you’re staring at a loaded barbell on the ground or an opponent in front of you, in both sports, the true fight is against yourself. You’re only using the external forces to test your limits and discover who you really are. That’s the only way you get better at anything.