Kindness toward parents sits in the Qur'an beside the worship of God, named in the same sentence and in more than one chapter. The placement carries the argument. What you owe your mother and father is set out as a matter of religion, and it holds on the mornings when the feeling is there and on the mornings when it is not.
Much of what the Qur'an says here concerns old age. The scene is specific: one or both of them in your care, slower than they were, asking the same question twice. The first line drawn is at the sigh of impatience, well before anything larger. Then something warmer than restraint is asked of you, "lower to them the wing of humility out of mercy" (17:24), along with a prayer to say over them that reaches back to your own smallness.
The mother's share of this is told through the body: "his mother carried him through weakness upon weakness" (31:14). Gratitude to God and gratitude to parents arrive in the same clause of that verse, which is one way of saying the debt is real and has a date on it. If you are raising children of your own now, the verses on parenthood sit on the other side of the same ledger.
Readers come to this with every kind of story. Some parents kept their children safe, and some pressed their children toward things those children could not follow. The Qur'an takes that second case up directly. Obedience is suspended in the single matter of belief while the kindness is left standing, "yet keep them honorable company in this world" (31:15). Distance and honor are allowed to sit together, which is more room than most people are given.
The last thing the Qur'an does with parents is turn them into a prayer. Ibrahim asks forgiveness for his mother and father; Nuh asks it for his. For anyone whose parents have died, that part stays open, and it does not depend on what was said or left unsaid between you. The verses on grief may help on the days it lands hardest.
17:23 — Your Lord has decreed that you worship none but him, and that you treat your parents well. If one or both of them reach old age in your care, do not say to them a word of contempt, do not rebuff them — speak to them with honor.
17:24 — And lower to them the wing of humility out of mercy, and say, "My Lord, have mercy on them, as they raised me when I was small."
31:14 — And we have enjoined upon the human being concerning his parents — his mother carried him through weakness upon weakness, and his weaning is in two years — be grateful to me and to your parents; to me is the return.
31:15 — But if they press you to associate with me what you have no knowledge of, do not obey them — yet keep them honorable company in this world, and follow the way of those who turn to me. Then to me is your return, and I will tell you what you used to do.
46:15 — And we have enjoined upon the human being kindness toward his parents. His mother carried him through hardship and gave birth to him through hardship, and his bearing and weaning together is thirty months. Then, when he reaches his full strength and reaches forty years, he says, "My Lord, move me to be grateful for the blessing you have bestowed on me and on my parents, and to do righteous work that pleases you, and set right for me my offspring. I have turned to you in repentance, and I am one of those who surrender."
29:8 — And we have enjoined upon the human being kindness toward his parents. But if they press you to associate with me what you have no knowledge of, do not obey them. To me is your return, and I will tell you what you were doing.
19:14 — and devoted to his parents, never overbearing or defiant.
14:41 — Our Lord, forgive me, my parents, and the believers on the day the reckoning is established.
71:28 — My Lord, forgive me and my parents, and whoever enters my house as a believer, and the believing men and the believing women — and increase the wrongdoers in nothing but ruin.