West Ham boss David Moyes wants "calm heads" ahead of facing KAA Gent in the Europa Conference League quarterfinals.
Moyes was sent off in the Europa League semifinals last season against Eintracht Frankfurt, as was Aaron Cresswell.
"We have to learn where we can draw the line," said Moyes.
"Emotions are something you never know what's going to happen. Looking back I can understand it, we were right up against it on occasions, but we've got to make sure we are better disciplined, calmer.
"But we still want the players to be emotional, we want them to understand what it means, we want them to be motivated and eager to impress.
"We don't want vanilla players who are going to go around and not tackle, challenge, run hard, be competitive. You need players who are going to do all those things."
Moyes added, "I'd love to give the supporters another couple of nights like we did last season and I'd truly like to go further if we can.
"I've got big respect for Gent but I would do for all the teams we play.
"We've got no divine right to be getting through, we're going to have to work very hard for it, we're going to have to play well."