I can so feel your pain. Just couple weeks ago I lost a game (fourth rated long game I've ever lost) and my OTB rating dropped 13 points (2000 -> 1987). That was by far the biggest drop I've ever had.
That was also the second time in my life when I lost a rated long game against sub-2000 player. I am still quite shocked. I have to consider giving chess up altogether. Coz one thing is for sure; if I keep losing a game per year, I'll never make it over 2900.