Bottas replaced Nico Rosberg at Mercedes following the 2016 season but admitted that he struggled to cope with the pressure of competing against Hamilton for race wins.
Hamilton was the clear lead driver at Mercedes and won the world championship in four of the five seasons in which he and Bottas were team-mates.
And the Finnish driver, who left the team to join Alfa Romeo at the end of last season, said he was at his lowest point at the end of the 2018 season, when Hamilton won the title but Bottas finished fifth in the standings and without a race win.
“At the end of 2018 I almost stopped, it was so close,” Bottas said on the Motor Sport Magazine podcast. “Just because of the fact that I couldn’t understand and take the fact that I couldn’t beat Lewis in those two years.
“I put so much pressure on myself. Towards the end of 18, especially when I started to have the support role in the team, I really couldn’t take it, I really struggled. It was not fun.
“The last four or five races of 18 were more painful because you should enjoy F1 and it is pretty cool, but it wasn’t that at all. So I had a good break between the two seasons and really had to think things through.
“The human mind is strange in a way that sometimes you go into dark places. You lose the joy in things and I just completely lost the joy of F1 and racing in F1. I was almost angry at F1.”
Hamilton said prior to Bottas leaving the team that he was the “best team-mate” he has ever had in the sport. Hamilton has since been joined at Mercedes by George Russell, who is currently ahead of the seven-time world champion in the standings.
“Lewis had been part of [Mercedes] for a long time,” Bottas added when asked about what it was like to be the 37-year-old’s team-mate. “As a driver and, as a person in the team, he’s the dominant person.
“So it’s quite difficult to step up, and I never could really step up in a way that I wanted alongside Lewis because the team was so welded in, and… he’s Lewis. So it’s like, everyone looks up to him almost. So that’s how it goes.”