Gradually does it....over a period of months....
Warm up >stretch>do your training>stretch at the end of your session. Achilees tendon, groin, and hamstring are easy to damage if you rush into things and are slow to heal. Also take care of your knee joints if a lot of kicking is involved. You can probably tell how good your dojo is by the amount emphasis on wam up/stretch in it. Martial arts are not only about fighting but also about looking after your body and accepting its limits.