Start with simple straight in shots. Object ball on the spot, cue ball near the side pocket.
Shoot it at least twenty times, or forty times. Just a gentle stroke, draw back maybe six inches.
Settle for just making it at first, then concentrate on putting the ball in a certain part of the pocket.
You may have to experiment with head position so the shot goes where you are looking. That's the key. Your arm and your eyes have to point at the same thing.
Then move the object ball so you are shooting progressively longer straight ins.
I practice these for at least an hour, ending up shooting the cue ball from the kitchen, object ball one diamond beyond the side pocket.
Work on your stroke until you can draw the ball back to the end rail.
Then shoot it with follow. Set it up with just enough angle so you don't follow it in. With a nice easy stoke you should be able to pocket the ball and get the cue ball back into the kitchen. Do that for at least an hour.
Then I set up a row of five or six balls three diamonds from the end rail, cue ball in the kitchen. I shoot them all into the same pocket. Use a touch of outside to spin the cue ball out of the corner, trying for perfect two rail shape for the next ball. More hours, then switch sides and shoot into the other corner.
I don't get bored, I see it as a challenge, and it will really get you in stroke. If you can, do this for a few days by yourself, staying out of tournaments or challenge matches, then come back and smoke the competition.