From “The Little Prince” by Antoine de Saint-Exupery
" ‘It would have been better to come back at the same hour,’ said the fox. "If for example, you come at 4 o’clock in the afternoon, then at three o’clock I shall begin to be happy. I shall feel happier and happier as the hour advances. At four o’clock, I shall be already worrying and jumping about. I shall show you how happy I am ! But if you come at just any time, I shall never know at what hour my heart is to be ready to greet you…’ "
My reason for having a set time for practice, so that my heart is ready to greet the Self.