The Scarlets fly-half missed last season's RBS 6 Nations title success while he recovered from a ruptured Achilles tendon suffered on Heineken Cup duty against Exeter two weeks before Christmas.
Priestland returned to action ahead of schedule five months later, but an injury recurrence just before the Scarlets kicked off their RaboDirect PRO12 play-off against Ulster in May knocked him for six.
"I did have a little bit of doubt when the injury happened a second time," the 26-year-old said.
"(Wasps centre) Lee Thomas ruptured his Achilles a week before me, and he was great, sending me a message on Facebook.
"There are different opinions about rehab, and he was unfortunate in that he slipped in the bath a few weeks later and had to retire from the game.
"I had that at the back of my mind and worried if there was a real weakness which would mean the end.
"I saw the surgeon, and he said I had to extra careful, which is why I took my time.
"The night it went again marked the end of our season. Everyone went out in Belfast, and I was stuck in the hotel with no-one to speak to. I just locked myself away."
In Priestland's absence, Ospreys playmaker Dan Biggar expertly guided Wales along the path to Six Nations silverware, culminating in a record 30-3 victory over Grand Slam-chasing England at the Millennium Stadium last March.
Priestland also saw his hopes disappear of British and Irish Lions selection for the summer tour to Australia, but he successfully emerged through a dark tunnel of despair and now looks set for starting duty against South Africa next Saturday.
"It has not been the best of years for me, but you have to take the positives. I feel refreshed, and so does my body," added Priestland, whose last Test appearance came against Australia in November 2012.
"It is not the easiest to deal with an injury like that, but it is not the end of the world. I am just enjoying playing rugby again after being out for so long.
"It makes you reflect on things and you get to realise how lucky you are to be a rugby player and doing something you like.
"The toughest thing for me was the game in Ulster when I came back and the injury occurred again.
Having made two appearances off the bench (against Cardiff Blues and Treviso) I started against Ulster, and when it (Achilles) went I could not believe it.
"All the hard work had not been worth it, it seemed. But after the initial disappointment - I was down for a period - you try to forget about it, enjoy the summer and get back.
"I had six weeks off doing nothing at all, and that was probably the best thing for me because I came back refreshed and I look forward to turning up to training.
"It is such a big difference to 12 months ago, when my body was in bits and I did not enjoy turning up to work. It was a drag getting through training and games, but now there are no issues at all now and it is nice getting out of bed in the morning with your body feeling normal."
Top of Priestland's agenda will be to help Wales collect a long-overdue major southern hemisphere scalp, either against South Africa or when Australia arrive in four weeks' time.
Wales have not beaten the Springboks since 1999 - their solitary success against them - while it is five years since they lowered Australian colours.
"If we can reach the standard we set against England - and a lot of the boys did in the third Test in Australia for the Lions - we are a match for anyone and can dominate most sides in the world," he said.