The other 2 posters above me pretty much nailed it, but I'll add a little more information which is what I think you are really asking:
It may not be realistic to expect and achieve strength gains EVERY workout. Dave Tate took 5 years to break a bench PR, and he knows a thing or two about adding some weight to the bar.
The key is the increase the weight, the reps, the intensity, the density, etc... OVER TIME, which is where the progress happens. It might take your body a few weeks, a few months, or even a few years if you get REALLY strong to lay down the new muscle and neural adaptations in order to lift more than the last time.
So for a standard BBing workout it might look like this over the coarse of a few months for the incline press
210x5 (had a bad day, missed meals, over trained, whatever it is)
210x9 (stuck with it for a month, got weaker for a small period of time, but over all became stronger)
Its like the stock market, there are going to be periods of amazing progress, some periods of decline, but the goal overall is to go up over years and years.