I Spy on My Teenagers...

Sometimes I find myself sneaking into their rooms to see what's really going on in there. I look through their drawers, maybe peek at some of their texts or notes left out... It feels weird but also oddly comforting to know a bit more about them than they let on. I feel like I should tell them off for invading privacy if the roles were reversed, but then again, they're just teenagers and can be so unpredictable these days... Am I being paranoid? Is this normal behavior from a parent or am I overstepping my boundaries? Any advice would be appreciated...