Whether you succeed or fail depends on your own concentration. You have to realize what your own failings are. For example, at the end of the day I know I'm more tired and my serve is more likely to fall short. Instead of serving from 15 feet back, I move up to 5 feet. I don't serve down the right side line on a critical serve.
Some serves are inherently safer than others.
Aiming for the seam between the two passers is a pretty darn safe serve, and it's one of the more effective ones. The jump serve might give you an ace, but that floater will probably result in a mediocre pass, which will result in a predictable set to an outside hitter that you can probably block or dig. Once the ball's back on your side and under your control, you have the advantage. If you don't know what kind of serve to use in a particular instance, ask your captain, who should know all of the serving rules, and also understands your serving abilities.