Some excerpts from a fascinating book I'm reading which offers an exercise to consider about our tendency to interrupt:

"Step One - simply notice when you interrupt. Don't stop your interrupting, just notice it.

"Step Two -as you interrupt, silently say this to yourself: 'I'm not letting you fnished your sentence because ________' (and fill in the blank). This will hardly slow you down at all. Just watch, and let the blank fill itself with what you usually hide from yourself in the blur of conversation.