Crappy Days.

So as a rather depressing start to my blog, do you ever get that really terrible feeling that lasts for days and all you can think is 'I suck at everything'?
I think I'm in the middle of one of those stupid mindsets. It seems I am utterly incapable of the littlest things, and find myself gritting my teeth and giving myself an internal lecture about making myself useful. And then while I'm obsessing over everything I'm doing wrong, I cut one too many slices of tomato and think 'Man, i really do suck'.
I suck at driving, I suck at speaking coherently, I suck at cutting tomato for a salad, I suck at having a shower, I suck at buying the groceries, I suck at keeping a conversation without making it awkward, I suck at eating, cooking, talking, thinking, doing and being. I. SUCK.
I bet the word 'suck' just started to sound funny.
So with that said, what I'm interested to know is, how do you get yourself out of this ridiculous thinking pattern? Is it possible that one can simply, 'get over it'? And what gets our confidence down so low in the first place, eh? I imagine it could be a whole truckload of factors. Stress, family tension, a fight with a friend, a bad word from somebody, a rumour, the death of a loved one, or the repetitive making of a simple mistake.
The thing is, since I am coming toward the end of a very relaxing 3 month holiday, I can't seem to identify the cause. Let's put it down to boredom.