I've been known to beat up the squat rack after a failed attempt, or toss a plate or two around. But then again...I'm an asshole. I thought it was the gear when I was on it, but I've been natural for a year and I still do it. If I get all fired up to hit a PR, I can't fucking stand it when I miss it. I look around for something to break. I get furious at failure. Then because I'm foolish, I'll try again and again, and get even angrier.
Regarding the strength decrease, there's a lot of other variables that may be effecting you right now. School, work, female, bad diet, etc etc. If you tend to be angry in the gym, you may also tend to bring outside problems into the cage which is bad. Or you could just need a little break. Maybe a beach with an outstanding lady and some Corona would do the trick.