Roma had been 2-1 up at half-time in the Europa League semi-final, but crumbled for a 6-2 defeat.
“We made mistakes, I made a big mistake on one goal, and you pay for those at this level," Cristante told Sky Italia.
“When you go behind and are really eager to make up for it, all it takes is two or three unlucky incidents and you end up conceding this many goals.
“Having said that, we absolutely should not have played a second half like that and throw away everything we did before. There's nothing to salvage from that half.
“The incidents didn't help, but then we weren't solid in moments of difficulty. We could've held on longer when it was 2-2, but instead we continued to press high trying to win it and that was a mistake."