I used to do this all the time and STILL catch myself doing it a lot. I try to keep my body relaxed when I run and it makes running so much easier! I make sure my hands aren’t in a fist but that they are loose. I act like I am holding a quarter between my thumb and index finger to remind me not to squeeze. I also lean forward a touch and lift my chest up. Having the proper form and finding things that help you always make running more fun and easier to do!
thanks berry for the image