Daniel Ricciardo has revealed that he was at "such a low" and changed as a person during the 2015 Formula 1 season because of off-track factors, including Jules Bianchi's death.
Speaking on a special farewell Red Bull podcast after the 2018 season, his last with the team before switching to Renault next year, Ricciardo picked out '15 as one of his most significant memories.
Having come to prominence in 2014 by winning three grands prix in his first season with Red Bull and besting four-time world champion team-mate Sebastian Vettel, Ricciardo suffered a tougher second campaign at the team.
He was beaten by new team-mate Daniil Kvyat in the points and scored just two podiums all season, with the first of those coming at the Hungarian GP just days after Bianchi finally passed away nine months on from his crash in the 2014 Japanese GP.
"A lot happened in 2015, more on a personal level, with life," said Ricciardo.
"Jules' passing affected me more than I ever would have thought and I had a few other things going on in my life at that time that in a way shaped me into this next version of who I am.
"The first race back was Budapest and that was my first podium that year, a double podium for the team, and I remember the whole weekend was very emotional.
"To get a podium there felt massive, it was a huge relief and a moment of gratitude.
"That was really important. In 2015, that was a really big high to come off such a low."
Ricciardo returned to winning ways the following year and 2015 proved to be the only victory-free season of his five at Red Bull.
He leaves the team with seven wins and 29 podiums from 100 starts, although the 2018 season was bittersweet for the 29-year-old as poor reliability dogged his entire campaign.
Ricciardo revealed he had more off-track distractions again this year but believes he will be stronger because of that.
"I thought 2015 was challenging, on and off-track, but this year the on-track stuff's been more challenging than ever," said Ricciardo.
"Also just other things, a lot of people have been trying to help, [I've been] just trying to figure out who is really trying to help and who is not.
"There's just been a lot of other stuff.
"I know in the long-term, and my good friends around me tell me this, it's all part of the story and it's going to shape a beautiful ending one day.
"It sucks for the time being, but I believe that."