How do I stay calm instead of reacting with force?

You can steady most situations. It is the truly volatile ones that pull you toward force before you have chosen it, and you are honest enough to see it happening. That pull is not a character flaw. It is your body reacting to real danger faster than your mind can weigh it. But the fastest reaction is not always the one you would choose. Force feels like control, but often it is the opposite: it is what happens when the moment runs you instead of you running the moment. The volatile situations spike your fear, and fear wants to end the threat now. The skill is not to feel no fear. It is to buy a half-second between the feeling and the act, and to use that half-second to choose. So train the pause, not the reaction. Pick one small physical cue, a slow breath, your feet planted, that you do the instant you feel the heat rise. It will not make the danger smaller. It gives the calmer part of you time to arrive before your hands do. That gap is where your judgment lives.