I am looking for a TV series I saw around 2000-2005.
I believe it was about a secret organisation sending people in the past to prevent a disaster. I remember at the end of the episode, they were celebrating another successful mission - that person 5th or 10th - which was rare because all the other people sent before became insane after only 2 or 3 missions.
I do remember it because the main character was looking at a champagne glass, but the bubbles were going down, implying that mental health was degrading.