What it means is that we need to prioritize, to give each task the best effort we can and realize when we work that some tasks are just less important than others. This skill is very important for students, who sometimes choose to ignore sleep or meals to do assignments. Deciding which tasks are truly important is a vital first step in stress management, but just as important is a set of goals, a plan for accomplishing those tasks. A set of reasonable goals can help to prevent unreasonable expectations. Many people complain that they try to follow their goals, but end up frustrated and unable to complete the goals that they've set for themselves.
Frustration is a key sign of unreasonable goals.
It's not specific, has no way to measure success, doesn't mention any sort of action and does not give a timeframe. Depending on the circumstances, it may not even be realistic. Given my previous grades, an A is a little too much for this semester, but a B would put me on the right track. One easy way to improve my grades is to watch less TV and spend more time studying. When this happens, the first step is to try to decide what's actually the problem.