"In high altitudes, they put oxygen in my dressing room under the stage! This is me before the encore," Underwood wrote in the photo caption. She later tweeted, "Thanks, Colorado, for the wonderful energy over the last two shows! I can always tell when I'm in a great place full of great people."
Though the singer didn't get to spend the holiday with her hockey player husband, Mike Fisher still made the Oklahoma native feel special. "I got to my hotel room this morning to find roses from my sweet Valentine waiting for me," Underwood tweeted before taking the stage. "I am such a lucky lady! Happy V-Day everyone!"
Post-show, Underwood kicked back and watched the Fox reality show that made her a household name. "Watching Idol now on the bus thinking, 'Good Lord, what if they had sent me home?'" she tweeted. "It's crazy how a few key moments can change a life!"
During a recent CBS This Morning interview, Underwood admitted she still worries fans won't show up to her concerts. "We gear up for a big old tour . . . and I'm still thinking, 'God, are we doing this for a reason? Are people going to show up? Are people going to like it? Are people going to fill those seats out there? Or is this the wrong thing to do?'"
The 29-year-old "Two Black Cadillacs" singer added, "I'd rather doubt than be completely overconfident and have it blow up in my face!"
This article originally appeared on Usmagazine.com: Carrie Underwood Uses Oxygen Mask During Colorado Concert: Picture