Unless you're reading flash fiction, the protagonist will probably fail to resolve the conflict on his first try. There would simply not be enough story. That's where the try-fail cycle comes in.
Did you ever have to fill out one of those plot-arc diagrams in school? They never even told you that they were an arc and most of the time they were simply a hill that ended up a little taller at the right edge than the left. Most plots don't work that way. The plot is more of a series of hills getting progressively taller at their peak. Each time the reader thinks the hero (or anti-hero) will succeed they are likely to fail, dropping the tension for a while before sharply raising it again. Thus, he/she tries and fails in a cycle, hence the name. Eventually, the conflict will be resolved and the final hill will slope downward a varying amount (depending upon how much of the book takes place after the resolution).
The try-fail cycle is just one of several major plot types, but it is one of the more commonly stated forms. Use it wisely.