One of the most disappointing times in a new fencer's career is when he faces an experienced teammate for the first time in competition. Perhaps the new fencer waited before competing, and does extremely well in practice. Chances are, that new fencer is gonna get stomped, and hard.
What a lot of newer folks fail to realize is that while you are meant to practice hard at the club, the mentality and incentives for success (and disincentives for failure) are a lot different when the score is being written and published. I might give up on a 15 or even a 5 touch bout on a Friday night after a long week and all I really want to do is get drunk with my friends. On a Saturday afternoon when my coaches are watching and you are facing me in the first round of DEs - you're toast. It's not that I don't take you seriously in practice, it just doesn't matter as much if I don't. Some fencers, and athletes in general, cannot mentally make the seperation between competition speed and practice speed - others can.
One thing that does help is treating the practice bouts like a competition, or really just writing down the score. Not "keep score," but physically making a pool scoresheet and dutifully filling it in. Suddenly letting the newbie get three free touches isn't such a good idea any more. Even an adult like me who understands the psychology gets caught up in the faux competition. And even if no one cares a week after its over, winning that pool suddenly matters for that night, and now every touch matters.
God told Habbakuk to "Write the vision, make it plain upon tables, that he may run that readeth it." The idea was that if you write something plainly and clearly, the message will shine through to the reader and inspire him to act. If a new fencer needs a highly competitive fencer to give 100%, just ask that someone writes and posts the score - that will get his undivided attention.