O Allah, help me remember You, expressing gratitude to You and worship You in the best manner

There is no doubt that the Prophet, may the  peace and blessings be upon him, was keen to deepen the roots of love in the heart of Mu'adh so that he goes ahead in obedience to Allah - the Almighty - and walk on his straight path until he meets his Lord.
When the hand of Mu'adh, may Allah be pleased with him, was reassured in the hand of the Prophet, may the peace and blessings be upon him, and felt the coolness of his kindness. The Prophet`s heart expressed the inner feelings and normally the Prophet said: " By Allah, I love you ". Mu'adh rejoiced the paradise of love enjoys the grace of closeness to the closest servant to Allah the Exalted - and knows for sure that he Prophet, may the peace and blessings be upon him, "that one will be with those whom he loves.

 
After the Prophet, may the peace and blessings of Allah be upon him, informed him that he loves him, he advised him: "O Mu'adh do not to miss supplicating after every Salat (prayer) saying: 'Allahumma a'inni 'ala dhikrika wa shukrika, wa husni 'ibadatika,' (O Allah, help me remember You, express gratitude to You and worship You in the best manner".

That is, do not fail to say after every obligatory or voluntary this supplication with your heart and your tongue. The heart is the one who speaks and the tongue translates its feelings.
This supplication combines all good for the Muslim in this world and the Hereafter, it is one of the most comprehensive supplications instructed by the Prophet, may the peace and blessings of Allah be upon him.