I wish my horse was thick

[malibu211211]

I always said that Monty is the 'Tim nice but dim' kind of horse and that Donnegan was far too clever for his own good. Turns out Monty does have a brain and has decided it's time to use it

Took beastie in the school tonight and he went really well. Lots of energy, going nicely forwards...................then all of a sudden he found the Yak switch

Head in air, coming back at me, almost cantering on the spot, lots of energy just going nowhere

Have narrowed it down to my terrible canter transitions

I tense up when asking for canter and am restricting him with my body. Suggestions and help please