Farrell started the first match against the Springboks last month but was dropped to the bench for the second and third Tests.
England endured a 2-0 series defeat, drawing the third game, but Farrell has learnt much from the tour.
"The experience of playing in a series like that is what you benefit from most of all," he said.
"It's a massive challenge over there and we had three really tough games that could have gone either way.
"We can take a lot of confidence from that and the experience as a whole was totally beneficial.
"I didn't see any of the criticism of me. All I wanted to do was play and that pushed me on."
Farrell was speaking at Saracens' new home ground at Barnet Copthall Stadium, which is to be renamed Allianz Park.
The club agreed an £8million, six-year deal with Allianz that secures the German financial services provider stadium naming rights and shirt sponsorship.
Saracens hope to move into their new home in Hendon, north London, in February following a 15-year tenancy at Vicarage Road.
Watching their team at the home of Watford Football Club has not always been appreciated by Saracens fans, but Farrell will retain fond memories of the stadium.
"Vicarage Road is the place where I broke into the Saracens first team and I spent my first two seasons there," he said.
"We won the Premiership while we were playing there, which was a privilege.
"It's a pitch where you play rugby, it doesn't really matter what's going on around it.
"Although attendances weren't what we hoped, we're looking forward to the future and getting into this place.
"Having two home grounds this season won't be a problem. Hopefully we'll turn this place into a fortress and attendances will build and build."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.