I was once talking with a painting contractor friend...well, actually we were arguing...about the relative differences between a professionally done paint job and a DIY effort. I was sticking up for the latter, of course. Not that I have any problem with the pros, nor with anyone who wants to throw them some work.
The crux of my argument was that a conscientious DIYer could do just as good a job painting a wall as a conscientious pro. My friend countered that the big difference between pros and DIYers was that, for the former, the job was 80 percent preparation and 20 percent painting, while for the latter the figures were reversed. And, when that preparation gets reduced to nothing more than a brief bit of foreplay, the result is a paint job that will not last.
I agree with his point but would argue that no "conscientious" DIYer would take such a lackadaisical approach to preparation. But, truth be told, lots of DIYers aren't so conscientious. And nowhere are they less conscientious, in my experience, than when it comes to painting concrete—and specifically garage floors. Good preparation is critical to a good quality garage floor paint job. Concrete is porous, and therefore often too wet or oily to hold a coat of paint. And it is also often too cold and smooth.
That's why I often hear people complain about what a waste of time and money it is to paint their garage floor. They did it, and a year or two later the paint started peeling and chipping.
Others, however, have painted their garage floors and, years later, continued to marvel at the durability of the job. The difference between these two experiences is preparation. Read the label, follow the instructions and devote 80 percent of your time to preparation, and you will almost certainly find yourself in the camp of happy DIYer rather than whining DIYer.