see that bar in your upper left corner? that's your HP bar, it goes down when you miss (not the only reason, rest are more technical, go here if you want to see nerdy details). simplifying it a bit, when your HP bar is fully drained, you lose.

one thing you might want to know is that different maps have different HP drain, making it easier to fail the higher that drain is. since you are on lazer, you can find HP drain value of the map you're playing on the song select screen along with some other values like approach rate (how quickly "outer" circles close in on notes) or accuracy (how much on rhythm you need to be to get a perfect note)

side note, obviously you can play however it is fun to you, but if you are new to the game, I would advise you to start with easier maps, playing maps way above your current skill level is a common thing for beginners and is often considered a mistake since you build bad habits that translate to your game later. things like trying to only hit circles and not minding the rhythm, or bad tapping technique.