So I have been planning a major vacation for many months. Since I had plans so far in advance, I of course notified my boss that I wanted to take this time off. He told me it would be no problem at all so far in advance, and he would make sure I got my time off for the dates requested.
As the time for my break got closer, I reminded my boss of my eventual vacation. He reiterated that everything was taken care of.
Finally the time for my vacation arrived. My boss suddenly acted like this was completely out of the blue. He said I didn't request the time off in the “proper channels” and there was no way I could get the time off. There was nothing he could do, I simply had to come in.
I hung up the phone in shock. I sat for a few minutes and weighed my options. The plane tickets had been bought, the hotels paid for, the entire trip was planned. Not to mention this trip was very important for personal reasons regarding family. I decided I had no choice, I simply had to go on this trip.
So I called my boss back and said I would simply have to quit. He started to both get angry and to sound a bit panicked, which was strange. He demanded to know if I was giving two weeks notice. I told him I could give one weeks notice, since my trip was in a week and I simply couldn't miss it. He asked if I would stay if I got my time off, and I said of course. He said he would see what he could do and ended the call.
He called me back 10 minutes later and said it was all taken care of, and I could go on my trip.
These events made me realize a lot of things at once. One: my boss is an incompetent asshole who will try and screw me over, if it is convenient. Two: My boss actually desperately needs me to continue working for him and will pull strings, if it is convenient. Three: I can do better than this job and I should plan to move on starting now.
Remember that you often have more leverage than they want you to think you have.