Indulging Vs. Allowing

When a feeling or thought comes up that we are not in line with and we are watching it, sometimes more thoughts come up and continue to spin. If we are spinning and continuing these thoughts how is this different from allowing them to be (Feeling the feelings and allowing the thoughts to be there)? It sounds like the allowing could be a few minutes or a few days. How do we recognize we are indulging versus allowing to be there, if it lasts longer into the day (s)?