Is it considered ill-mannered to say, "For my sake, O Lord" in supplication (du'a), and what is the ruling on saying, "O Lord, by the right of any good deed You know I have done for Your sake"?

When making supplication (du'a), a Muslim should know that Allah is aware of their condition and what is in their mind, and that He is more merciful to them than a mother is to her infant. If they ask Him sincerely, while observing the manners of du'a, their supplication will be answered. It is better to avoid the phrase "by the right of the status of so-and-so" and replace it with the forms of tawassul (seeking nearness to Allah) mentioned in the Quran and Sunnah. Tawassul through righteous deeds is permissible.