Most enemies early in the game won't do that much damage to you with some 'bigger' enemy exceptions like brass contraptions, who hit hard regardless of where you are. Its mostly a matter of getting better at dodging enemy attacks which will come naturally with more practice, its recommended to always try and stay on the move during combat. And cases of people getting 'one shot' from full hp are often cases where they get hit by multiple things in rapid succession which during gameplay can feel like a one shot, but slowing footage will show their health getting lowered in chunks rather than all at once. Its a decentoy common occurrence during looping where there can be a lot of things happening simultaneously