Despite Kris Doolan heading the Jags into the lead at Firhill, Kenny McLean's penalty just before the break was enough to earn a point for Danny Lennon's side.
Both teams had chances to win it and give their hopes of SPFL Premiership survival a major boost in the second round of post-split fixtures.
But McMillan reckons a share of the spoils was a fair result as Thistle followed up their win over Kilmarnock with another solid showing.
He said: "It was very hard but then again it always is at this level. It was a good result in the end though.
"We just need to make sure we're taking points out of every game so that we don't lose ground on those around us and we can secure our position in this league as soon as possible.
"We dominated in the first half and it was very disappointing to lose a goal so late on, particularly to what I think is a fairly soft penalty decision.
"It's always a risk when you take that chance and tackle like that but again you do feel hard done by. Sometimes they go for you and sometimes they don't but we'll dust ourselves down. I consider that a very hard-fought point.
"I thought we might have just nicked it at the end there - I fancied us.
"I suppose there were chances at both ends, they hit the post, we had one off the bar and there were a couple of good scrambles, but it just wasn't to be.
"We were happy with how we performed, we defended well and I think a point was probably justice for both sides."
Having taken four points from their first two post-split games, Thistle are 10th in the standings with just three fixtures to go this term.
Ross County's weekend win over Killie saw Allan Johnston's side drop into the play-off place but the race for safety is still far too close to call.
The Jags head to Easter Road this weekend knowing victory would be a major step in the right direction, and McMillan is only focused on what Alan Archibald's side need to do to survive.
He said: "We don't need to worry about the other results just now, we [did enough on Friday night] and it's a very important point.
"It might have been different if we hadn't won last week but four points from two tough games is a very good start to the run-in.
"We're just taking it a game at a time at the moment and now we're all focused on taking maximum points away from Easter Road.
"It'll be tough over there but it's a great opportunity to build on a solid start."