It was only after he skipped international friendlies against Australia and Uzbekistan in November that Son found his goalscoring touch, finding the net nine times for Spurs over 12 appearances in all competitions.
"I was tired after the Asian Games because in that tournament it was playing after (every) two or three days," the 26-year-old said.
"It (November) was a turning point for me because I was tired and I didn't travel. It was good to have this time, some days off, and hard sessions with the team."
South Korea are one of the football powerhouses in Asia, having competed at the World Cup nine consecutive times starting in 1986. But they have won the Asian Cup title only twice, with the latest victory in 1960.
Since coach Paolo Bento took charge of the Taeguk Warriors in August, they have been unbeaten in seven matches, building optimism ahead of their opening group stage match against Philippines in Dubai on Monday.
Son will, however, miss South Korea's first two group stage matches against Philippines and Kyrgyzstan under an agreement between Spurs and the Korea Football Association.
He will join the squad in time for their final group C clash against China on Jan. 16.
"It is very important to be right mentally at the Asian Cup and to come back with a strong mind and be strong physically," he added.
"The Asian Cup is big for us because we have not won it for 59 years. I'm going there not just to enjoy it, I am going there to win something and come back with confidence."
(This story has been refiled to fix typo in headline.)
(Reporting by Hardik Vyas in Bengaluru; editing by Sudipto Ganguly)
