The major problem was the number of tasks in progress. There were just too many things ongoing so that control could easily get lost. Fortunately things were sorted out a few days later. Lots of things done and few things in progress:
After a while I recognized the repeating problem of too many thing in progress. After a short personal retrospective I decided to improve my focus on the "in progress" lane. It seemed obvious to limit the number of things to work on in parallel. I splitted the "in progress" lane in two parts:
a) an "on hold / wait" part for all the things that have been started but need external help
b) a "working on" part with focus on all the things in progress. This part now is a Kanban box with a limit of two tasks.
The positive effects of this change appeared instantly: things got their focus on the essence! Tasks were done in a much more sustaining pace than before.
I am curious about the next improvements of my personal task board. Let's see what my next retrospectives will expose.