The speed and spin you use as you hit a ball makes a difference.

Here you might expect a 30 degree rebound off the rail since the ball goes into the rail at about 30 degrees, but the collision induced spin usually makes the cue ball come off closer to 45 degrees and head right toward the side pocket. All of us have scratched doing this. Hitting a little harder or with a little draw can change the angle off the object ball from the 30 degree rolling collision angle and avoid the side pocket. Adding outside (right in the case) english can also keep you out of trouble but usually causes the cue ball to go further than a natural hit. Using inside (left here) english will usually cause the cue to go less distance along with changing the angle. A really thin cut (since you're so close to the pocket) doesn't transfer much of the cue ball energy to the object ball and allows you to get back down the table without hitting too hard. If you don't want to go back down the table you can cheat the pocket the other way and hit it real full transferring most of the energy to the object ball. Of course, if you are too straight and try this, you might end up following the ball in the pocket and scratching. Using draw and right english here can keep you out of trouble.