Today I've got a sudden revelation about the way I usually get to program. Not that it wasn't obvious before but this time I've managed to formulate this with actual words.
Often I'm facing a problem of not being able to start programming something big: a big new subsystem, a deep refactoring touching almost all the files. Even when such a thing is in progress and spans several days it's hard to get back to the daunting work on the next day.
Apparently what's needed here is a thing with which everyone who ever did any sport exercises is familiar — a warm-up. I noticed that it's easier to start working on the same codebase with something insignificant and not scary: do some simple renames, write or edit a couple of docstrings, fix-up some package dependencies. These things help to acquire back certain feel of the project's domain, remember some thoughts that I had last time when I was working on it.
Hope this helps someone too :-)