When there's a task that needs to be done, we shouldn't say it's impossible and won't be accomplished. This is a negative approach and might even hurt you, G-d forbid.
Making an effort is always better than not doing anything because at least you tried, and nobody can accuse you of not doing so. Sometimes though, there might be a situation where you have a delemma and there are pros and cons to both doing it and not doing it. In this case, we need to think about which situation would have the worse consequence, doing the task or not.