Composing what I can't improvise...

As I was working on an arrangement of Tom Bahler's hit song "She's Out Of My Life" (which was made famous by Michael Jackson) I realized that I particularly enjoy writing music, which I wouldn't yet be able to improvise. That way, composing is a process of pushing the boundaries of the inner sense, trying to reach for musical ideas I most likely wouldn't attain in a playing situation, where the music would have to blossom in the moment. Composing thus becomes a mental workout, preparing the mind to fetch more distant material faster, and teaching the soul how to feel it and appreciate it...