#showtooltip Ice Nova
/cast [harm] Ice Nova
Watching top Mages play on Twitch, and I'm obviously not comparable to them in any way, however I've noticed A LOT of Mages ( in the heat of the moment, obviously ) failing their Ice Novas during high intensity situations on high rating.
This is obviously not their fault as the ability is piss poor coded and will automatically cast on yourself the moment it can't cast on your target, however just use the above macro and you'll NEVER waste Ice Nova stacks.
( the only problem might be using it on crystal, as it's neutral ( yellow ) target instead of hostile ( red ), but in that case you can add another like with /cast [target=Temporal Crystal] Ice Nova or something )