Imam Ahmad once asked his students: "Do you know whose supplication Allah accepts?"
They said "Tell us".
He said: "Do you know the man in the middle of the ocean, on a ship that has broken down, clinging to a piece of wood with the waves crashing down upon him seeking to bring him down? So the man begins to cry and invoke Allah saying 'My Lord, My Lord'."
So, he continued, "Were any of you to invoke Allah like that man your Dua' would certainly be accepted by Allah!"
And Allah says:
أَمَّن يُجِيبُ الْمُضْطَرَّ إِذَا دَعَاهُ
"Is He [not best] who responds to the desperate one when he calls upon Him?"