Houllier said: "I don't know whether what happened to Glenn is stress related, but all I know is this job is getting more and more difficult. I started as a manager in 1973 and got to the top level in 1978. Ever since then, everything has changed -- the media, the pressure and the demands for results.
"Even here at Liverpool that is the case. We have won six trophies, played Champions League football twice and won the UEFA Cup, but it is still not enough. People always want more and patience is not part of the modern game any more.
"You need to have a good board of directors and players who will give it their best shot in every game. You also have to keep believing in yourself, which is sometimes difficult because the pressure comes from lots of things.
"That makes the job more difficult -- and even if we look relaxed and comfortable, we don't know what is going on inside the body."