A short and simple Sutta is now provided that teaches gentleness in your practice. Do not stop during difficulty, but do not strain at the leash. Progress is made by steady effort only.
This is the Oghataraṇasutta, the Sutta appears in the Samyutta Nikaya, and in English it is called ‘Crossing the Flood’.
Saṃyutta Nikāya 1.1
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Crossing the Flood
Thus have I heard. On one occasion the Blessed One was dwelling at Savatthi in Jeta’s Grove, Anathapiṇḍika’s Park. Then, when the night had advanced, a certain devatā of stunning beauty, illuminating the entire Jeta’s Grove, approached the Blessed One. Having approached, he paid homage to the Blessed One, stood to one side, and said to him:
“How, dear sir, did you cross the flood?”
“By not halting, friend, and by not straining I crossed the flood.”
“But how is it, dear sir, that by not halting and by not straining you crossed the flood?”
“When I came to a standstill, friend, then I sank; but when I struggled, then I got swept away. It is in this way, friend, that by not halting and by not straining I crossed the flood.”
“After a long time at last I see
A brahmin who is fully quenched,
Who by not halting, not straining,
Has crossed over attachment to the world.”
This is what that devatā said. The Teacher approved. Then that devatā, thinking, “The Teacher has approved of me,” paid homage to the Blessed One and, keeping him on the right, disappeared right there.
Source: Sutta Central