Reaching goal weight and weight fluctuations

Can you explain again about weight fluctuations? I reached my goal weight and am proud of myself. I like seeing that number every day. Now when it fluctuates above by 1/2 or 1 pound I feel a bit disappointed. My weight coach said it is not just what you ate the day before, but maybe what you ate that week. What do you think about weight fluctuations? Btw, I am working the thoughts around seeing the bump up.