The yoyo not only needs practice (there is a technique) but you need to be mentally focussed and ensure your diet and fluids are bang on. It is a maximal test. The pass mark of 18.2 seemed insane when I set out on the journey at first, I was getting 16.6 consistently and was shattered and frustrated. But as I worked on the turning, almost sprinting off from the line to gain momentum, changing push off leg and turning leg to distribute the pressure etc I started getting better scores. Then ensuring pre-test diet and that I am fully hydrated makes a big difference. Then, finally, it's all in the head. Trust me, mid 17's is really tough but there is no way you are giving up then and that's what gets you through.