Andy Robinson's side had earlier disposed of Australia and Fiji in their previous two Tests of their summer tour to erase memories of their winless Six Nations campaign.
And Harley admits the mood in the Scotland dressing room has changed and they can continue to look forwards instead of back.
"I always felt we were going to make the breakthrough," said Harley. "Even though Samoa were playing so well and they'd had the pressure, we got down on the 22 and we kept the pressure on them.
"It was a brilliant feeling to get the cap and to score the winning try as well was just a dream. It's been an incredible tour."
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