Harrington, who is now out of action after slipping on the stairs at home over Christmas and breaking a bone in his wrist, said: "Obviously I'm thrilled to be named as Ryder Cup captain for 2020, it's not something I went into lightly".
The Dubliner will lead Europe against the U.S. at Whistling Straits next year.
The appointment of the three-time major champion, 47, was announced in a news conference at Wentworth on Tuesday.
The objective will be to keep the trophy that Thomas Bjorn's men claimed so masterfully at the Le Golf National just outside Paris in September 2018.
Despite his anxieties, the Ryder Cup has adorned European trophy cabinets more often than American ones since the tournament was revamped in 1979.
"I can go back as far as Sam Torrance and Woosie [Ian Woosnam], who were very emotional, put their arm around your shoulder and made you believe that they believed in you". "I don't think I ever thought I wasn't going to do it, but I wanted to make sure I was doing it for the right reasons".
"I think the standard of golf on the European Tour and the players we have on tour is going to ensure that". I want to hopefully leave the Ryder Cup and the European Tour in a better place after two years.
"I will definitely take bits from all of them".
Harrington has been encouraged by what he said was the "unanimous" support of Europe's players.
Six of the last seven contests have been won by the home side and, as Harrington himself has pointed out, it took a "Miracle at Medinah" for the one away victory to occur.
He has learnt from some of the great European captains and golfing figures - Bernhard Langer, Colin Montgomerie, Paul McGinley - and said he will take little bits from each in a bid to maintain Europe's dominance in the event.
"Great news to wake up to", said Donald, who played on three Ryder Cup teams with Harrington in 2004, 2006 and 2010.
"And secondly the course is a European-style of course, it's windy and has a links-feel to it".
Couples captained the USA to three straight Presidents Cup triumphs from 2009 to 2013 and was a vice for the next two, but in 2017 he stated he felt his opportunity to oversee a Ryder Cup had "passed by". "You just have to know the man behind the scenes".
"I'm excited with the whole idea, I hope I can add something to it", added Harrington.
"I know there's words there, but the actions nowhere near match up".
"I remember getting scalded on one of the team meetings for laying up into a hazard".