The 49-year-old described his side's performance as "outstanding", but confessed that the series has been tough due to the criticism he has received over his team selection.
"I've got very mixed emotions. The last three or four days have been pretty hard. It was a tough call to leave Brian O'Driscoll out," BBC Sport quotes him as saying.
"You always doubt decisions you make, but you have to make those hard calls. I have taken a bit of flack.
"It was about the boys today and winning the series. It was an outstanding performance. We started well, came under some pressure and bounced back."
The Lions ran in four tries at the ANZ Stadium in Sydney to record an historic 41-16 victory over the Wallabies.