Allah the Exalted says:
Say, "I am only a man like you, to whom it has been revealed that your god is but one God; so take a straight course to Him and seek His forgiveness." And woe to the polytheists.
On the authority of Thawban, may Allah be pleased with him, who said:
The Messenger of Allah, peace and blessings of Allah be upon him, said:
"Strive for uprightness, though you will never be able to encompass it all."
Meaning: strive for uprightness in every matter.
Exert your utmost effort in maintaining this uprightness as much as you are able.
Even if you do not attain perfect uprightness,
It is for this reason that seeking forgiveness is prescribed to compensate for any deficiency.
Ibn al-Qayyim, may Allah have mercy on him, said:
"Acts of disobedience cause anxiety, sorrow,
Fear, constriction of the chest,
And diseases of the heart.
There is no remedy for them except through repentance and seeking forgiveness."
Ibn Rajab al-Hanbali, may Allah have mercy on him, said:
Regarding the saying of Allah the Exalted:
"So take a straight course to Him and seek His forgiveness,"
It is an indication that there will inevitably be some shortcoming in the uprightness one is commanded to uphold.
Thus, this is compensated for by seeking forgiveness,
Which necessitates repentance and a return to uprightness.