Noob macro question

Hey guys. Leveling up my mage as Arcane and holy shit is it stronk. Anyway, I made a macro to use my PoM(makes next spell insta cast) to make my Arcane Blast insta cast

/cast Presence of Mind /cast Arcane Blast

boom, works. but I have to be standing still. If I just hit the binds for PoM and AB normally I don't have to be standing still. 1. why is this? 2. is there a way to fix it so I don't have to stand still to use it? I really am a macro noob.

Also, anyone that's good with macros:

My main is a 100 PvE Ret paladin and i'm also leveling a 46 Mut rogue. Any good macros I should have/use, and if you don't mind, what are they?

Thanks a ton ahead of time!