Rasulullah Sallalahu alayhi wa Sallam used to recite :
أستغفرالله ~ Astaghfirullah (I seek forgiveness of Allah)
at least 100 times a day.
Hazrat Abdullah bin Abbas Radiyallahu Anhu narrates that Rasulullah Sallallahu Alayhi Wasallam said:
“The one who [regularly] says Istighfaar, Allah Azza Wa-Jal will open a path for him from all difficulties, remove him from all sorrow, and grant him sustenance from unimagined and unexpected sources.”