Let's talk about young horses. 

Young horses who are high octane sportscars.

Young horses that like to GO.

I watched this video, where a young mare (with a go button) was being worked on a lunge:

Lunging the Explosive Young Horse and Improving the Canter - BONUS FOOTAGE LIMITED TIME from Manolo Mendez Dressage on Vimeo.

For me there were several gems at the very end - about young horses having a lot of fire, and about supporting and going slowly, so you don't crush the brilliance out of your horse and turn them into something ordinary (totally paraphrased there).

This came in handy when I finally made it out to the barn after finally defeating this epic cold (hooray!) When asking for the trot (verbally) Tesla got excited and offered some lovely canter under saddle, very round, she was carrying herself, rather than throwing her head down and chugging away on the forehand.  
Her canter can be tough to sit (think: pogo stick) but this was much more balanced and quiet.

This isn't what I asked for, but I didn't want to discourage her trying, so we practiced walk-few trot steps- to canter then slowly down back to trot in both direction, in big round loops around the arena (and lots of "good girl").

Mental note to self: don't always ask for the canter every time we do trot work
(otherwise she starts anticipating like crazy!)

and if she is offering something lovely, time to work on that :D