Robert Kubica says he is "positive" even though he has dropped off the F1 grid for 2020.
2016 world champion Nico Rosberg, who assisted Kubica as he bid to resurrect his career in the last few years, admits he was "surprised" with the Polish driver's disappointing return to Formula 1 last year.
"I'm surprised he couldn't get closer to (George) Russell," he told Auto Hebdo.
"In talent and his attitude, Robert was never inferior to Hamilton. But I did not take into account the influence of the eight-year break.
"Just imagine if Roger Federer did not play tennis for eight years and then he came back," Rosberg added.
Kubica, 35, will stay in the paddock as Alfa Romeo's reserve driver this year, combining that with a race seat in the German touring car series DTM.
Another half-day in Alfa Romeo's 2020 car may also be planned for this week in Barcelona.
Kubica told Eleven Sports in Barcelona: "Life has taught me that you cannot plan either good things or bad things. So I don't plan anymore.
"Replacing Jacques Villeneuve in 2006 was not planned. And in 2011, within a minute, I lost what was already planned," he said, referring to the crash that left him with permanent injuries.
"When I became reserve driver at Williams, it turned out to be very positive even if you are mainly watching the other drivers as they race.
"But I have changed my attitude completely. You can see other drivers who are on the bench that they are rarely positive, but I think my attitude has worked so far and that's why I approach my role very positively," Kubica added.