You can see the Performance Meter at the top of the screen while playing a track. It's basically your HP. Do not miss notes or it will drop low and you'll be in danger of failing. Easy - Hard tracks are rather forgiving compared to Insane ones, but be car
Once the Performance Meter drops to 0, you fail the track and you need to start over.
You gain life from : Hitting a hit circle, hitting a slider start, end or return tick, spinning and completing a spinner and continue to spin the spinner.
You lose life from : Constant life drain, missing a hit circle or a slider, not completing a spinner an d not spinning after you completed your spinner.
You reserve life from : Break time and Spinning after you completed your spinner.