A record crowd of 8,855 watched on at Scotstoun as Gregor Towsend's men edged past rivals Edinburgh, 37-34, to claim just their second bonus-point win of the season and take a huge step towards securing a home semi-final play-off spot.
The win also meant that Glasgow were crowned 1872 Cup winners for the fifth year in a row, but 31-year-old Cusiter warned that his side must keep their focus for the remainder of the season.
"It was really important to win the game in terms of the league, and we also got the bonus point so from that point of view we're really happy," he told Glasgow Warriors TV.
"It's in our hands now to secure a home semi-final. We go to Treviso next week, that's a tough place to go but we know that if we keep winning and we get one more bonus point then it's a home semi-final. That's obviously the objective."
The home side raced to an early lead as Peter Murchie first touched down before Ruaridh Jackson and Mark Bennett scored tries of their own.
Edinburgh responded through Willem Nel and Matt Scott and skipper Greg Laidlaw added 14 points from his boot, but Glasgow's Peter Murchie then crashed across the whitewash for his second of the game before Rob Harley gave his side a 17-point-advantage at 37-20.
And that proved to be the decisive try as they held off a late rally from Edinburgh's Tomas Leonardi and Tim Visser to claim a memorable victory.
"We played a defensive style and played really well," said Cusiter. "We scored some really nice tries but it was too intermitent, we probably dropped off at times and made too many errors in defence.
"I think there are elements of the game that we weren't happy with. We dropped our intensity at times and Edinburgh played well to be fair.
"It was a disappointing finish to the game as we allowed them a couple of tries at the end. But it's a tough one, they're always tight games and overall a 3-point win, we've got to be happy with that.
"They played a bit more rugby than we were expecting and caused us a few problems. The games are coming really thick and fast so we have to recover and go out and do it all again.
"We want to raise our level of performance each week and we have two big games to go. Overall it's job done and we move on to next week."
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