Figure out the enemy elements (use the battlenote item to find enemy weaknesses) and use armor/buffs to counter their elements. This alone negates like 80% of the damage you end up taking, same stuff for status effects.
To give an example, after level 25 most enemies will start to heavily use attacks that drain MP instead of dealing health damage, and at 0 MP your character will die. You have access to a buff (exorcist's barrier) that reduces MP damage taken and that turns a 20-40 damage hit to MP into a 1 damage hit.
Keep an eye on the topbar too, and think about equipping a tome of turmoil to weaken enemies and buff your own attacks even further.
If you're missing skills look at what you can craft or go back and do treasure stuff.
To give an example, after level 25 most enemies will start to heavily use attacks that drain MP instead of dealing health damage, and at 0 MP your character will die. You have access to a buff (exorcist's barrier) that reduces MP damage taken and that turns a 20-40 damage hit to MP into a 1 damage hit.
Keep an eye on the topbar too, and think about equipping a tome of turmoil to weaken enemies and buff your own attacks even further.
If you're missing skills look at what you can craft or go back and do treasure stuff.