How to join DELTA FORCE*

This big 17hh 8 year old has had some issues and has had a few people off so he was sent to me to bring back into work. I have been long lining him and started gently hacking him where he’s been very brave and confident walking and trotting, however when standing and walking on again - he has been launching himself forwards. We have been working on this with improvement, asking him to walk forward into a light contact instead of launching, until today when he decided he couldn’t cope any further