Consider the following diagram that represents the spectrum between two dimensions; Skill Level and Challenge Level.

As you can see, you will be in a state of flow when your skill level is high and you are adequately challenged. On the other hand, you will be relaxed if you are highly skilled, but not challenged and so on with other traits as shown in the graph.

Apathy is a state of indifference where emotions such as passion, motivation and excitement are suppressed. An apathetic person may appear extremely boring to others, someone to avoid at all costs. You want to avoid this state as much as you can.

As you can see in the graph, to get out of apathy, you need to either challenge yourself or work on your skills to improve them.  The problem is that, if you challenge yourself a little, you start to get worried while if you just work on a skill without any claim or challenge, you can quickly get bored again and get back to apathy.

Your ultimate goal is to get to the state of flow and to get there you need to both challenge yourself and improve your skills in line with each other. Only that way you can hope to get to your most productive state or peak performance.