The Scots prevailed on penalties in Belgrade after a 90th-minute Luka Jovic header cancelled out Christie’s 52nd minute opener.
However, goalkeeper David Marshall was the hero as he saved Aleksandar Mitrovic’s penalty as Scotland won the shoot-out 5-4 and secured their berth at next summer’s championships.
Christie had to watch the equaliser, extra time and penalties from the bench after being replaced three minutes from the end of regular time and admitted that it was one the hardest moments of his career.
"It's an amazing night," said the Celtic midfielder, who missed last month’s matches due to coronavirus isolation protocols. “I think from the start, we believed. From the camps previously, we've picked up so much belief in each other.”
When asked what it was like to watch the penalty shoot-out not being involved, Christie admitted: "It wasn't nice. When you're on the pitch, you always feel you can impact it, but when you're off, you can't watch it - it's horrible. Those penalties are probably the worst thing I've ever been through.”
Welling up on camera as he spoke to Sky Sports, Christie added: "It's for the whole nation. It's been a horrible year for everyone [with the pandemic]. We knew that, coming into the game, we could give a little something to this country. I hope everyone back home is having a party. We deserve it."