In my experience, slumps can occur for a variety of reasons. The best thing would be to
hook up with a competent instructor . A competent extra pair of eyes can usually spot the problem (s) much quicker than trying to go it alone. In the process, going this route can often shorten the amount of time it takes to correct the issues giving rise to your slump.
As an aside, a lot of very good advice has been offered about the values of the "free swing" and most of it is true. A free swing, and one that is synchronized with the footwork, will greatly assist in you in your ability to repeat quality shots. As a result, I always strive to maintain as free and unrestricted swing as possible. However, there are
times when for me, the "free swing" is NOT the best route to go. this usually occurs when I am facing a very difficult lane pattern where the margin of error is close to nil. At other times, my body simply refuses to cooperate with my brain. When this happens, I find it helpful to deploy some muscle in my swing while simultaneously slowing the tempo of my footwork.
Also, on the subject of overthinking. It is my belief that the more natural talent a bowler has, the less thinking they have to do. Most elite bowlers have such superb
physical games (even though many of them do not do it by the "book") that they do not have to worry as much as the rest of us about "timing", or other physical aspects of their game. Mother Nature has blessed them in ways that we can only dream of...
I am in that roughly 97%+ of the bowling population that has to continue to focus on aspects of my game that the 3% do not.
For me, natural tempo and flow takes constant and persistent effort. Over the years, I have tried to do most of my thinking
prior to getting up on the approach. On only my best days, does this work for me.
Yes, I still try to not overthink, try to develop a smooth, free swing approach and when I can do it, the results are good. However, bowling often puts hefty demands on our bodies, making next to impossible to at all times, be able to execute with
the grace and effortless precision we desire. There are times when some of us need to resort to our own Plan B, a plan that might go against bowling orthodoxy but one that fits our personal physiological makeup, and one that gives us a BETTER chance at success on any given day. If this means that I have to push, pull, "fit" or muscle, in order to score on days when the conditions or my body will not permit me to do otherwise then I will do it with absolutely with no qualms or reservations.