The Finn endured a difficult second campaign with Mercedes in 2018 as he struggled with reliability issues.
While Bottas failed to make an impression, team-mate Lewis Hamilton went from strength to strength as he secured a fifth world title.
With a host of young drivers pushing for top seats this season, Bottas' position at Mercedes was thought to be under pressure if he continued to under-deliver.
But he made a sensational start to 2019 with victory at the Australian Grand Prix, finishing almost 21 seconds ahead of Hamilton.
Bottas says his attitude has changed for the campaign, while also joking his new facial hair could be behind his winning start.
"It's obviously very early in the season, it's one race, but I can for sure say that something in my mindset has changed for the year," he told a media conference on Thursday.
"The preparation over the winter and just the way of how I feel and think about things has changed.
"It's quite difficult to explain in detail but I feel different to years before."
'It must be the beard...’
Don’t you dare even think about trimming it, Bottas! #BahrainGP #VB77 pic.twitter.com/f2rj4qjsOI
— Mercedes-AMG F1 (@MercedesAMGF1) March 28, 2019
He subsequently added: "It must be the beard!"
Bottas has finished on the podium in Bahrain over the last two seasons, and he hopes to continue that run on Sunday.
"It's normally been quite a strong race for me but obviously every year it's a new race, and you still need to go off quite well," he said.
"I think racing here, this year, might be a bit better in terms of overtaking with the new DRS zone so I think still, ultimately, the race pace is going to be important.
"But it's been a strong race for me personally in the past and I rate it quite well on my list but obviously the aim is to approach every weekend knowing and aiming to be on top of your game and not to have any bad races anyway."