"It was challenging to come back after the success of Beijing. It was hard to find the motivation," 23-time Olympic gold medallist Micheal Phelps said on Tuesday about the most challenging phase of his illustrious career. "That and coming back for Rio, it made the journey so much better."

Speaking at the launch of sportswear brand Under Armour's first store in New Delhi, the most successful Olympian of all time said that announcing his retirement after the 2012 Olympics made his comeback at 2016 Games more memorable.

At the age of 31, Phelps returned to the Olympic pool and won five gold medals and a silver.

"In terms of stats, obviously it had to be Beijing because I won eight gold. But Rio was the climb of the mountain. One of the most enjoyable rides for me. I felt like a 16- or 17-year-old all over again. I loved the process," he said.

Though Sydney 2000 was his first Olympics appearance, Athens four years later was the beginning of his gold rush, where he announced himself to the world with six gold medals and two bronze.

"When I get into the pool, I don’t have the same feel. I have lost it! No comeback, guys. So, don’t ask that question," said Phelps, as he emphasised that his fascinating journey as a swimmer, that included 39 world records and and 26 gold medals at the World Championships.

Addressing young Indian athletes, Phelps said it was important to always keep training and wished them luck for the Tokyo Olympics.

"Never give up on anything you dream. If you truly want it, you can make it a reality. My life is an example. It was not easy, it was not fun. Never miss training, and never give up. I had no opportunity to
give up on training. Listen to your coaches. Train well. Hope to see you in Tokyo," he said.

"It is all in the six inches between the two ears, whether it is golf, tennis, basketball, cricket, soccer, football. Performing at that one moment is the challenge," said Kevin Plank, the founder of Under Armour.

When Plank queried, Phelps said he hated losing more than anything else, but was never afraid of defeat

Recalling the most common question about what was in his mind when he was ready to jump into the pool for the races, Phelps said that there was nothing.

"You can’t change anything. It is what it is," said Phelps as he pointed at the need to stay cool while jumping into the pool, focusing on the process and executing to the best of one’s ability.

Phelps stressed that training was everything, and that if he missed one day, it meant two days of training to get back to the same level.

"I did it for 16 years, six days a week," he said.

Talking about his famous arm clap, before the start of the races as he prepared for the jump, Phelps said it was a normal routine for him, and he was fascinated to observe how it brought so many different feelings among fellow swimmers lined up for the race.

He repeated the drill on stage, swinging his arms and clapping, much to the cheer of the gathering.

Having enjoyed an extraordinary career in swimming, the 33-year-old Phelps who is married and has two children, said he was continuing with the mission on various other fronts such as water safety.

"It is a fun next journey for me. Let us see where it takes me," he said.