A smooth stroke is a worthy goal; you will never be good without it. A little wiggle at the back end will translate into inconsistency and many missed shots for unknown reasons. You knew the aim was good and it looked good but missed by a mile.
One practice shot is to place the CB (cue ball) on a spot, hit it to the opposite cushion and see if it comes back and strikes your tip or goes off to the side. It is a good idea to place a piece of chalk at the opposite end with a corner facing you. This will give you an exact point to aim at. If the CB goes off to the side it means you did not hit the exact center of the CB and the resulting english pushed it off center when it hit the cushion. This is also good practice for your follow through, staying put after the stroke.
A second shot you can do is very easy and can be used to correct your stroke occasionally during play. Place or pretend place the cue ball on one spot then aiming directly at the other spot or center diamond and just stroke but not strike the ball. Once you feel your stroke is right and feels good, look down at the diamond below your stick as you stroke and watch your cue go back and forth over the diamond. Is the cue directly over the diamond or is it on a slight angle? It should be straight. Is the cue moving back and forth straight or is there a wiggle? I find this a good way to get your stroke back in shape at any time; it only takes a few seconds. You can get the smooth feel back without the wiggle.
A third practice shot is to place your CB about ½ inch away from a side cushion (right if you are right handed) about 1/3 to ½ way up the rail then do the practice stroke. You can observe you cue movement along side the cushion. It should remain ½ inch away from cushion as you slide back and forth. If you see your cue moving all around concentrate on making it go straight and do it for a little while to get the feel of it and to train the muscles to do this.
Also, follow through on your shots, stay down after you stroke. It assists in a smooth stroke and is often one of the most neglected aspects in shooting. If you watch the pros you will see they have follow through. Many so-called good players have not figured this out and they look like a jack-in-the-box. This is part of what makes a pro look smooth.
What it amounts to is practice, lots of practice. Mosconi did not become Mosconi by being a weekend warrior. The more practice the faster you will get the stroke in shape. The above practice tests will assist but it still takes game practice to get the feel. If you play long enough over time the cue will actually feel like part of your arm. Most pool players never get to this point.