transtemporal
Explorer
Sacred flame to kill a kobold who does 1d4+3 damage, is better than spending a spell slot to heal for 1d4+3. Next time you see a girl about to be smashed, don't think "oh crap, I need to save my slots to heal", instead cast sanctuary, command (flee), or silence. You get more milage out of it.
Totally, the best defense is a good offense. Healing should be an emergency option when everything goes south.
Life cleric being an exception.
And even then, I still think its more efficient to attack even as a life cleric (unless you're roleplaying a pacifist or something).