The world champion missed out on another day of running in Bahrain on Saturday when electrical and battery issues with the RB10 meant he first stopped on an installation lap, then failed to get out of the pitlane when Red Bull made a second attempt to begin its programme.
Vettel's problems came after Red Bull managed an encouraging 66 laps with his new team-mate Daniel Ricciardo on Friday.
Bahrain test day three report
"We thought we would be in a much better place this week compared to last week. That hasn't really been the case," said Vettel.
"There's no point being too emotional at this stage. We really have to take it step by step.
"We know how serious it is, especially inside the team - on Renault's side and our side. We've been a team the last five years and things have been fantastic.
"There were difficult days and difficult times - when we had the engine blow up with two races to go [in 2010], nearly deciding the championship, which wasn't great. There were other faults on our side, and on the driver's side. We are a team. These things happen.
"There's no reason to paint everything black. We know that it's a difficult time but everyone is aware of that and motivated to get out of it, get going and find out where we are."
F1 testing in pictures
Red Bull's problems have been exacerbated by the second and third tests taking place back to back so far from the team's European base, reckons Vettel, giving it little chance to recover from earlier faults.
"I think some things will calm down just by the fact that in two weeks' time we'll have lots of new parts," he said.
"Obviously we've had quite a lot of problems and therefore damaged quite a lot of parts which are not available overnight, and also we are in Bahrain so it's not that easy to fix things. That will get better once we get to Australia."
He also believes the RB10 has decent potential when it is able to run cleanly. "With the very, very few laps we did, the car felt good," said Vettel.
"I was very happy with the car. "Obviously it's a step back from last year in terms of overall grip, but it wasn't too bad.
"There's hope on that front."
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