How did Douglas make sure that he conquered the old terror?

Even after the swimming training was over, Douglas wasn't confident about his swimming or that he had overcome the fear. He was determined to completely get rid of it forever. He swam alone in the pool. He went to Lake Went worth to dive. There, he tried every possible stroke he had learnt. He fought back the tiny vestiges of terror that gripped him in middle of the lake. Finally, in his diving expedition in the Warm Lake, he realized that he had truly conquered his old terror.

Douglas still felt terror-stricken when he was alone in the pool. The remnants of the old terror would return, but he would rebuke it and go for another length of the pool. He was still not satisfied. So, he went to Lake Went worth in New Hampshire, dived off a dock at Triggs Island and swam two miles across the lake. He had his residual doubts. So, he went to Meade Glacier, dived into Warm Lake and swam across to the other shore and back.Thus, he made sure that he had conquered the old terror.