Level Up! Data Pack 1.20+

Level Up datapack will make you spawn with 3 hearts, which can be increased by increasing your experience level, to do so simply butcher a bunch of sheep and get their exp, also even if you want to cheat and give yourself EXP through commands it won’t work, so you’ll have to earn it through combating vicious enemies, but be careful not to approach enemies with higher experience level than you are.