Your legs are first thing to go and get tired when you start fight training.
You become fatigued and stationary.
It starts bad habit of never moving. You need to start doing a lot of circuit plyo work.
I will show you one of the training routines you can implement right now...
3 Exercises:
Do all of these as a circuit. One exercise after another until all 3 are complete. Then rest and repeat.
For a complete fight cardio program you can follow, see "Sprawl and Brawl: Solo Fight Cardio Training Program". It will help you develop killer fight cardio anytime, anywhere with no equipment and only 15 min per day and 4x per week.
Fight Training From Home Programs/Courses
Whether you are a professional or a beginner, you'll be spending majority of your life training solo (from home or on the road). Working on technique, drilling, developing strength and cardio. I've been training all my life. Here are some of the best programs and courses to start or continue fight training from home.