Sīdī Aḥmad Zarrūq writes:
Know that repentance is key, mindfulness of Allah is vast, and uprightness is the source of rectification. Meanwhile, a servant is never free of blunders, shortcomings or lassitude. Therefore, never be neglectful of repentance; never be remiss in your return to Allah; and never neglect acts that bring you closer to Allah. Indeed, any time you are remiss in fulfilling any of these three duties, still repent and return; anytime you err, hear and obey; anytime you fall short or burn out, do not give up.
The Counsel of Sīdī Aḥmad Zarrūq.
Agenda to Change our Condition, p 74.
A universal piece of advice for when the going seems to get tough, so that we keep on going, keep on working hard iA.