you sleep. that's how you heal. the temples don't sell or offer healing.
go to a safe place, like in the armory in arnika. antone's bedroom door closes and he's outside always guarding it, anyway.
plus, he's got a great chest for storing all your extra junk in.
the various fountains offer very limited healing. usually about 20-60 points worth. and it's usually in 1 point increments, so you do a LOT of clicking. so far, none of them have refilled since i wore them out.
there are a few fountains that give you relief from conditions. the one near lord braffit in the temple of arnika does. but it offers even less healing points than most of the regular founts.
and don't rest the full 8 hours. rest until everyone's health and mana bars are recharged. then wake them up.
to rest, click the "fire" icon in the lower left of your main game screen. to wake up, hit "C" or click on the bar at the upper right, where all your group spells are clustered. if you don't sleep the full 8 hours, you won't need to recast all your "walking around" spells every time you wake up. saves on mana. and it has you ready to go, in case you walk out the door and turn the corner into a face full of uglies.
well, i think that musta exhausted the subject of resting. 
V***V