Is habits a naturally normal thing

Ok, so I have a habit of biting my lip or playing with my nails; either when I'm nervous, or lying. Why does everyone have habits. from biting your nails all the way to picking your toes. Some people it may seem to be disgusting or filthy. but to us its like a stress reliever. it's like it calms us down, or distracts us from whatever bad happens. basically something that we get high off? i'm pretty sure when you guys read this i will sound so dumb. But fine, Okay, I'll admit when i bite my lip i don't necessarily bite my lip skin off or drink the blood? but sometimes it gets annoying when your friends or family look at you like a crazy person, when your scratching your nose, or constantly blinking. like what? i cant be doing anything wrong.I did have to find the strength to give up one of my main habits, biting my nails.(basically what almost everyone that i know does) which to me wasn't as big as i thought it was until i realized how embarrassing it is when you paint you nails, or scratch your back when you have little nubs.. XD or when people grab your hands. (Btw i use to hate that.....ALOT). but then i finally realized a few years later. What the heck!! my body i do what i want. until i realized when i was biting my nails i also was biting into my flesh. i literally had to give that up instantly. But hey whatever works for you. But when i gave up nail biting, constantly kept biting my lip until i accidentally busted it. okay habits can be bad or good..right.? so i got into drawing on my school desk but i realized this wasn't a good habit because i had to keep cleaning the desk. :( (XD) so i just decided i'll go with twirling or playing with my hair which hasn't led to do any damage YET. but doesn't everyone have a habit. but it is normal right?