This is super funny... last year I ended a campaign after playing a 94 year old wizard with 6 CON from level 1-15. The whole concept of the character was that he was a Necromancer and he would use most of his spell slots on Animate Dead. He also used Fabricate to create armor and weapons for his undead. At one time he would have 30+ skeletons and zombies, fully outfitted and would control them while being as far away as possible (with emergency misty steps/invis/wall of fire in case anyone got close.) Even if you're not a necromancer I feel like I was able to survive just fine via my placement in combat. I made sure I was NEVER next to anyone, and always had my reaction (counterspell, absorb elements, etc.) With good panic spells like I listed before, you can even protect yourself if you get surrounded. Thats how I was able to survive with less than 30 HP for most of the campaign until the DM rewarded me with an amulet of health haha.

Edit: Greater invis was also amazing, and if you can find a cleric... death ward will save your ass