Long time Pal/Lock player seeking for mage advice

I have been playing Warlock & Paladin for several years now and I recently leveled up a mage because I find it more appealing nowadays than my warlock. The thing is, I must not have the right reflexes nor habits when playing my mage because I get absolutely crushed in seconds and that is a bit irritating as I was playing Hpal at 2.2+ months ago.

I would love to hear about any tips & tricks you can give me, thanks in advance! :)