Why can't i break anything on minecraft?

Why can't i break anything on minecraft? - 1

Added (1). yes i'm holding down the left key and i'm not on adventure mode. It just randomly happened and i don't know what to do.

Well everything in the mimecraft world is destroy able. So either your game is broken. Or you are not doing it right.

Maybe just do /gamemode 2 and make sure you are not in adventure mode? Try restarting the game or make sure your not in a server as alot of stuff is unbreakable in servers