Ditch it = 1) throw it away, or 2) forget about it, similar to "drop it"

ditch it = get rid of it

"Ditch it." = Lose it fast (because we don't want the police to find it in our possession). "Ditch" has interesting associations. "Let's ditch school." = Let's skip school (and go to the beach instead). "Let's ditch him." = Run away and lose him (for example, your little brother), so he can't ruin your fun with your friends.