surroundings, and much else that is purely external, have, in general,
an important influence upon our mood and therefore upon our thoughts.
Hence both our view of any matter and our capacity for any work are
very much subject to time and place. So it is best to profit by a good
mood--for how seldom it comes!--

_Nehmt die gute Stimmung wahr,
Denn sie kommt so selten_.[1]

[Footnote 1: Goethe.]

We are not always able to form new ideas about; our surroundings, or
to command original thoughts: they come if they will, and when they
will. And so, too, we cannot always succeed in completely considering
some personal matter at the precise time at which we have determined
beforehand to consider it, and just when we set ourselves to do
so. For the peculiar train of thought which is favorable to it may
suddenly become active without any special call being made upon
it, and we may then follow it up with keen interest. In this way
reflection, too, chooses its own time.

This reining-in of the imagination which I am recommending, will also
forbid us to summon up the memory of the past misfortune, to paint
a dark picture of the injustice or harm that has been done us, the
losses we have sustained, the insults, slights and annoyances to which
we have been exposed: for to do that is to rouse into fresh life all
those hateful passions long laid asleep--the anger and resentment
which disturb and pollute our nature. In an excellent parable,
Proclus, the Neoplatonist, points out how in every town the mob dwells
side by side with those who are rich and distinguished: so, too, in