The Leicester Tigers man was out on loan at Nottingham four years ago as he was coming to terms with a change in position, and only made his Red Rose debut last November.
The 26-year-old will now start for the Lions against the Wallabies in the first Test of the series on Saturday, and he is determined to give his all for the cause.
"Even at the beginning of this season I wouldn't have even thought about playing for the British and Irish Lions," said Youngs. "It is a dream come true. It is quite hard to take in at the moment.
"But when I am standing in that changing room and running out, words cannot describe probably what will be going through my head and my heart will be pumping. I cannot wait for it. You have to prepare yourself for however long you can go for. I'm going to go as hard as I can for as long as I can.
"When my engine runs out or when the coaches feel it's right to pull me off, Richard Hibbard will come on. He's a great player, he will come on and be very physical and do well. The set piece in any game is massive, but there is going to be an extra edge to it. We are all really looking forward to it and cannot wait for the battle to come."
The opening Test gets underway in Brisbane at 11.05am.