Start by getting plenty of sleep in beds you own since that's gonna fix you up best and restore that max health too when you're really banged up watch out for sleeping in random beds though since guards might catch you. Marigold Decoctions are your best friend for quick healing, especially the strong ones that'll even cure hangovers when you need it just remember they work over time not instantly. Always carry bandages cause bleeding will drain your health fast and you definitely don't want that in the middle of a fight. Food helps in a pinch but stick to fresh stuff from butchers and grocers, spoiled food's gonna make things way worse trust me.

Bathhouses are great when you've got the coin, fixes you up and keeps you clean which actually matters for healing better especially with that Next to Godliness perk. Speaking of perks, grabbing Fundamentals of Medicine makes sleeping way more effective and Water of Life helps those potions work better too might be worth investing in those early on. When you're really hurt though just find a bed and sleep it off no point trying to tough it out and risk dying with valuable gear.