You know it's the Bonk when...

This summer I joined my family for a weeks holiday in the Alps in Bolzano so I brought my roadbike along.
I went for a great ride one afternoon, got about 70/80 miles in with some tough climbing, great descents and beautiful views and got back to Bolzano just about empty but good enough to have a quick post ride beer and cigarette in the main square.

The problem was that our hotel was just outside Bolzano at the top of a hill which is either reached by a 9/10km gut buster of a climb or by cable car and as I had done the climb the last couple of days and was pretty exhausted, I thought I would get the cable car. Obviously, I missed it by 10 minutes and as it was getting dark and my phone had died I had to ride up.

FUCK! about halfway up it was pitch black, started raining and there was thunder and lightning. I was totally fucked, nothing left in the legs and had to lie down by the side of the road about 3 or 4 times to try and recover. It took me bloody ages to get back and when I finally did, I dumped the bike outside the hotel, staggered through the full restaurant white as a sheet, dripping wet in full lycra, went to my room, turned the shower on and passed out.

Never have I been in so much pain

You've hit the nail on the head there. You know that you're bonking because you would like nothing more than to have a lie down by the side of the road to recover.