I remember how awkward and unnatural it felt when i made the transition from heel striking to fore/midfoot striking. I was born as a heel striker, i had no choice in that. It felt like i was tripping myself up and my studs were scuffing on the ground every step. After about 6-10 runs it started to normalise a bit, your body just naturally adapts and your brain constructs neural networks to improve you bit by bit. Now i have the choice of heel or fore/mid foot, i can choose whichever i think is best and may switch several times a second.