I will quote some expressions in his own words.

It was extremely cold, and I wished him to put on a great coat of mine which was in the boat: 'No, I am not cold; my anxiety for my Country will keep me warm.

Do you not think the fleet has sailed ?' 'I should suppose not, my Lord.' 'If they are, we shall follow then to Carlscrona in the boat, by G--d!'-- I merely state this to show how his thoughts must have been employed.

The idea of going in a small boat, rowing six oars, without a single morsel of anything to eat or drink, the distance of about fifty leagues, must convince the world that every other earthly consideration than that of serving his Country, was totally banished from his thoughts." Such preoccupation with one idea, and that idea so fine, brings back to us the old Nelson, who has found himself again amid the storm and stress of danger and of action, for which he was created.
About midnight he reached the "Elephant," where his flag was again hoisted; but he did not escape unharmed from the exposure he had too carelessly undergone.

"Since April 15," he wrote several weeks afterwards to Lady Hamilton, "I have been rapidly in a decline, but am now, thank God, I firmly believe, past all danger.