James Costello and Krista D'Agostino
Courtesy Krista D'Agostino
12/17/2013 AT 05:15 PM EST
There's a light at the end of the tunnel for Boston Marathon bombing victim James Costello.
Eight months after the horrific tragedy
, Costello, who suffered severe burns on his right arm and leg, is engaged to a nurse
he met while in treatment at Spaulding Rehabilitation Hospital.
"April 15 was one of the worst days of my life. I soon wondered why and for what reason this has happened," Costello wrote in a Facebook post.
Costello had been waiting at the finish line when the bomb went off, leaving him in need of multiple surgeries. For two weeks, he stayed at Massachusetts General Hospital before transferring to Spaulding Rehabilitation Hospital, where he met nurse Krista D'Agostino.
"After sharing a handful of conversations I realized not only how beautiful she was, but also what a kind heart she had," he wrote. "I somehow convinced her to attend a benefit with me, which turned into a few dates, which turned into a few inseparable months."
The couple are spending part of December in Europe on an all-expenses-paid "Heroes Cruise" with other victims and first responders. Costello revealed on Facebook that he asked D'Agostino to marry him in the French city of Lyon.
"I'm happy to announce that we will spend the rest of our lives together. I now realize why I was involved in the tragedy. It was to meet my best friend, and the love of my life," he wrote.