One day a student stopped me in the hallway and nearly cried out with anguish after receiving an undesirable grade, "But I worked so hard!" To the student, this statement should have caused me to reconsider my grade. I recall how frustrated she was when I informed her that she was confusing personal evaluation with professional assessment.
What's the difference?
To answer that question, let's first consider the fraught process of evaluation. This sort of measurement usually mixes belief and attitude. In other words, I may believe that I have completed four of five scheduled tasks today. This is a matter of fact. Yet I may also consider an attitude (mine or an attitude held by another person) about those tasks, whether, for instance, they were done "well" or "poorly." In this way, evaluation adds an attitudinal statement of good or bad, adequate or inadequate, positive or negative. Reasonable enough, right? At the same time we should remember how this process often dredges up deeper notions of worth ("Just how good an employee (or teacher or writer or whatever) am I?" This sort of character judgment can be useful.
Still it's generally better to assess rather than evaluate.
To assess is simply to compare outcomes to expectations, seeking to focus on observable characteristics rather than abstract responses: How many widgets have I completed on time? Can my students demonstrate their grasp of today's lesson? Do these paragraphs advance my central argument? Immediately you might be tempted to fall into the mode of evaluation after assessment: How "good" is the outcome? Shifting to that query makes sense when you are concerned both with "What is?" and "What should be?" This is the sign of a morally engaged life. However, "What should be" is seldom under our control. Thus we may understand Voltaire's wisdom when he wrote, "The best is the enemy of the good." Sometimes it's enough to take meaningful steps toward an ideal state, pausing occasionally to assess your progress without judging your distance from your goal too harshly.
Want a concrete example? Consider the fact that most weight-loss experts recommend you to avoid stepping on the scale every day when trying to shed excess pounds. They know how hard it is to separate the observable assessment from the emotional evaluation. If the scale doesn't show a lower number today, you may give up tomorrow. That's why experts in diet and nutrition typically encourage us to assess our physical health (which only partially includes numerical weight) in concrete ways rather than abstract measures. Do you feel comfortable in your clothes? Can you climb stairs without losing your breath? Is your body sufficiently able to fight off disease? Whether it's losing weight or gaining value, focus on the real rather than the ideal. Check the scale from time to time, but don't fixate on your distance from the ideal.
Of course, that's easy to say and hard to do. We're wired to evaluate; consequently we can easily sink into despair when things go wrong (as they frequently do). Few people are ever good enough to satisfy their ambitions. But anyone can say, "I will complete this task without error, starting one step at a time. First, I will understand how to gather my materials. Then..." This gradual accumulation of observable experience is the subject of assessment and, most importantly, the sign of growth. Even more, it helps us maintain our equilibrium when we might otherwise feel buffeted by evaluations, those of others or those presumed of us.
Want to get something done? Focus on what you can see. Look more, judge less.