Goals from Victor Wayama and Gary Hooper helped Neil Lennon's side move four points clear at the SPL summit with a game in hand.
It was the Hoops' first home league win since victory over Hearts way back in early October.
Mulgrew believes it's the perfect platform into the festive card of four games in 10 days, starting with Saturday's visit of Ross County and said: "Our aim and our belief is to put a run together now. The festive period is always vital and we have four games coming at us thick and fast and it is vital we use this win as a springboard into them.
"St Mirren came to Parkhead and tried to make life difficult for us by sitting in but we got two goals, should have scored more and also kept a clean sheet and that is very satisfying.
"In any league campaign your home form is vital and it was very important for us to get three points and the win against St Mirren.
"We have now opened up a four-point gap on Motherwell with a game in hand and that is a very good position for us to be in at this stage of the season.
"It's up to us to kick on from here."
Meanwhile, boss Lennon has revealed that he is still hopeful that star duo Gary Hooper and Victor Wanyama will pen the new contracts that have been tabled to them.
He said: "I don't think there is any doubt that Gary has enhanced his reputation here by quite a way and really made the most of his chance of playing in the Champions League.
"I'm not saying he owes us anything because he doesn't but I think, in the short-term anyway, it would be good for him to take the contract.
"There is still a bit of mileage in it but I don't think we're far away.
"With Victor if we can talk with his representatives again we will but that's been maybe a month or so ago now and we've not heard anything back from them."