Maybe you need a small heads up how health works in this game.
You get a bit of health for each 100 and 300 you hit. 300s give more health than 100s. 50s don't give any health. Misses reduce your health. By a lot more if it's a slider because sliders can be partially hit, even if you missed the sliderhead.
Very important to know is that you gain bonus health at the end of each combo (indicated by color/numbers).
If you managed to hit all 300s in the combo, you get a big chunk of bonus health. If you hit a 50 or missed in the combo, you get no bonus health at all. If you had a mix of 100s and 300s you get a small amount of bonus health.
Overall that means that it is very easy to recover from a miss if your accuracy is good enough to regularly obtain bonus health.
On the other hand it means that you will slowly but surely drain out of health if you keep missing or getting 50s for an extended period of time. It is likely not the health loss from misses that gives you trouble but your inability to profit from any of the available bonus health in higher SR maps.
Given this, I have to say that your statement about "only doing 300s and perfect sliders you still loose HP" is plain wrong, you will always be at max health with that. If your accuracy is 95% after a miss it means that you were already partially struggling before that.