Re-reading Marcus Aurelius’s Meditations the other day, I took new meaning from this entry:
Sober up, recall yourself, shake off sleep once more: realize they were mere dreams that troubled you, and now that you are awake again look on these things as you would have looked on a dream. (6.31)
You could use this technique when you realise you’ve been worrying (the worst kind of daydreaming). “Recall yourself” and treat those worries as you would treat dreams, i.e. don’t give them too much credit. There are, after all “more things … likely to frighten us than there are to crush us” Seneca reminds us, “we suffer more often in imagination than in reality.”