Pressley stepped up from his coaching role following the exit of Eddie May on Thursday and listened to chairman Martin Ritchie stressing that relegation would be "disastrous". Pressley goes into his first game against Hearts with the club three points adrift but he pledged to keep them in the top flight.
"I take the job with the belief I will keep them in the SPL," Pressley said. "If I don't do that I will have failed. That's football, that's life. You are always judged, you are judged by results."
He added: "It is a great degree of responsibility but I'm happy living with that.
"I believe in the players, I really do. I train with them every day, I have watched them closely, I see their character.
"They are a smashing group of players and I believe they are far greater than their league position suggests.
"I need to get inside the players' heads, need to make sure they know the demands of playing at this football club and start creating a winning mentality. We managed to do that at Hearts, it took a bit of time, but that's what I want to achieve here."
Alex Smith remains as assistant with Lee Bullen promoted from youth coach to working with his fellow first-team players.
And Smith has tipped Pressley to be an instant success. "I have had experience of this before with Dundee United," the 67-year-old said. "At this stage of the season we were seven points behind St Mirren and finished five points above them. I know what it needs to escape.
"The fans behaved like they had just won the cup - you can be a hero by keeping a club in the league."