This reminds me of the time when I was like twelve and I decided at like 2pm that I really wanted some private time in my bedroom. Like, time was a-wastin'.. Problem was, my bedroom door didn't lock and my mother was home. Fortunately, mom was outside doing some yard work. Unfortunately, I was a fucking idiot and decided the best way to deter her from walking in on me would be to go find her in the yard and announce to her just how very incredibly tired I was, and how important it was that I take a nap right at this instant, and how it would be best that she not come into my room and disturb me from my slumber so that I may enjoy this important time of sanctuary.
Fortunately, mom didn't walk in on me jerking off, but I remember her expression incredibly well.