Succumbing to a distraction in itself is not the culprit. It is why you distract and what you learn that determines the actual result.
Some days and some weeks may take you away from your goal. This can happen for many reasons. The question to ask is whether the shift of focus happened to do even more important work because an opportunity presented itself unexpectedly. If so, great! If not, ask what could you have done differently in the circumstances or how could you prevent this kind of distraction in the future.
If you have done something more important because of an unexpected opportunity or learned how you could do better next time, you are in the right direction. If not, avoid that habit. However, no matter what, do not panic or punish yourself. Instead, start fresh!