The 2014 Asian Games bronze medalist got the biggest blow of his career when he had to be hospitalised in Luzern, Switzerland after being diagnosed with pulmonary embolism, a condition where blood clots form in the veins of the patient causing breathing trouble.
The Olympics was just fortnight's away and there was speculation that he will be replaced by Sanjeev Rajput in the Rio-bound team for the two events of 50m prone and 50m 3 positions.
"Gagan Sir was of great help in Switzerland when I fell sick as we were training together," Chain told PTI.
Gagan will also compete in the two events apart from 10m air rifle.
Also Read
"Gagan Sir is not a rival. He is our senior teammate, a friend and a great person."
"My prayers to God gave me strength and I became okay. Deep inside, I had a firm belief that I would shoot in Rio, it's my dream. I more hungry now and will win an Olympic medal for my country," he added.
"I was sad when I was hospitalised but next day doctors told me there would be no surgery. There was a thought once that if I fall seriouslly ill I may not be able to shoot. But the doctors told me that I would be able to shoot within a week," Chain, who won six gold medals at the South Asian Games earlier this year in Guwahati, said.
"Although I am on medication but I am feeling better. After a long flight to Rio, I am taking rest and gradually getting back my rhythm. I feel fit and fine."
But his real journey began with his bronze medal win at the Asiad, Incheon-2014 and the next year he won a gold medal at the International Shooting Competition of Hannover in May 2015.
In three months' time, he booked his ticket to Rio at the World Cup in Gabala, Azerbaijan.
"Olympic Medal is my biggest dream and I want to achieve it this time," Chain, who booked an Olympics berth by finishing eighth in the World Cup, said.
"My journey to Olympic participation has been very enjoyable, I participated in all World Cups, I was given opportunity to buy my own rifle, ammunition and kit. My scores have also improved a lot, though I missed the medals narrowly in the World Cups."
The Naik Subedar of the 13th J&K Light Infantry, Chain is latest to represent at the Olympics from the Army Marksmanship Unit in Mhow, which has produced silver medalist duo of Rajyavardhan Singh Rathore (Athens-2004) and Vijay Kumar (London-2012).
This time, Mhow will have representation from shooting sensation Jitu Rai (10m air pistol, 50m pistol), Gurpreet Singh (10m air pistol, 25m rapid fire) and Chain.
On the secret of success from Mhow, he concluded stating: "The training we receive at AMU makes us the winners. We have world class ranges, best weapons, ammunition and testing facility there plus we see champions like Vijay and Jitu everyday. He is always of great help both off and on the field, I have learnt so many things from him.