This is a theory presented by psychologist Mihaly Csikzentmihaly in this book.
The Theory of Flow is best presented in graph relating the challenge of an activity to the skill you have/cultivate.
To present this theory, I am going to start with the graph below. Challenge on y-axis and skill on x-axis.
Point a in image below represent anyone who is just starting a new activity. Put it as an example, badminton. Say you have never played badminton before, and you go out there playing with your buddy who is similar as you, never had played before. You guys practically have zero skills and the challenge is zero. No competition whatsoever.
You start at a.
Say 20 years later you guys have both played the Olympics and you guys have the highest skills possible and facing the highest challenges, you got to point b.
Now there are these areas to the left (above) and the right (below) of a and b line.
You are in the area above the line if you don’t have a lot of skills but you’re facing big challenges. As an example, the second time you’re playing badminton suddenly your opponent is Lee Chong Wei (the number 1 player today according to BMF World Ranking), you’re in the zone which is obviously not good. Csikzentmihaly address this area as ANXIETY.
In simple words, ANXIETY is anything above the linear line that put you in a high state of challenge while your skill is low.
If you’re in the area below, you have the skills but you got not much challenge. Imagine you are Lee Choong Wei playing with a newbie, who only had only played badminton for a week. Csikzentmihaly address this area as BOREDOM.
Csikzentmihaly suggest that these two areas aren’t the optimal experiences in any aspects of life, be it at work, sports, leisure or relationships, you don’t want to stay in these regions.
You should stay on the a-b line.
The best thing that Csikzentmihaly propose is that you start the activity at point a, two players. The two play each other for a week (point c), time by time both gets better at the same time gets higher, keep going (point d), keep going (point e), until a year both are pretty good and about the same skills (point f).
This is a humongous dynamic momentum that pushes both towards betterment of the activity.
Csikzentmihaly address this as Flow Channel and this is one of the good way you should be approaching your activities in life.