CONCORD, N.C. (AP) — Kyle Larson spent a year preparing to run the double.

Instead, he got to run only a single, leaving the NASCAR star beyond disappointed.

Larson’s quest was to complete — if not win — the Indianapolis 500 and Coca-Cola 600 on Sunday, joining Tony Stewart as the only drivers to do all 1,100 laps in a single day. But then rain intervened not once but twice, and a rookie mistake at the Indy 500 cost him a chance to contend in the one race he ran.

“What I thought could be one of the best days of my life quickly turned into one of the most disappointing ones I’ve ever experienced,” Larson said on social media Monday, roughly 12 hours after storms in Charlotte prevented him from climbing into his No. 5 car to finish the NASCAR race.

When rain pushed back the start of the Indy 500 by four hours, Larson’s team made the decision to stay and run the race. He made a mistake going through gears at one point, costing him 10 spots, and his pit-road speeding penalty ended any chance of winning. He wound up finishing 18th.