Why does everyone feel the need to teach me about life?

im 17 everytime i tell my mom something like oh my freind lied to me, shell be like oh theyll be plenty of freinds like that throughout your life. And if i go this is hard, she goes oh life is hard, then my bf says hes smarter than me because he knwos more about life than me (hes 20) so its really anoying how everyone thinks if im young that means im dumb, im very mature for my age, its anoying i want them to shut up!