The question is -- Why is this so hard? Why do we touch things multiple times?
Think about some emails you receive .... emails that invariably sit in your inbox longer than they should .... emails that you glance at multiple times. This may be because:
1.) You are not sure what to do with it.
2.) You are sure what to do with it, but you need it to stay there to remind you later "what to do".
3.) You are waiting on someone or something else before you take action.
These examples are all inputs that need to go into your "system". Unfortunately when an input comes to us in the form of an email we forget about our "system" and work within our email "system".
Let me explain that a little better with an example: If someone (let's call him Ted) walks into your office and requests you to attend a meeting next week, but you are still not sure if you are going to be on a business trip, you must DO something with that request. "Ted I'll have to get back to you ..." (and you make a note somewhere, put it on a list, make a to-do, etc. so you will know to get back to Ted)
However, if someone sends you an email with the same request to be in a meeting next week, the very same meeting that you are not sure you can attend yet, many of us have conditioned our self to simply leave the email in our inbox. There it is - instead of putting it into your system, you have made your email inbox work as an extra part of your system. Now you have multiple systems!
Put another way, it's as if you told "Ted" to just stay right in your doorway and continue to ask you to attend the meeting UNTIL you are able to get back to him. Poor Ted! He is going to get tired standing there with his mouth open, but Ted actually becomes part of your system because you know he will be there!
So challenge yourself to "process" your emails and take the actions to where they need to be (a to-do list, action list, your calendar, etc.) -- YOUR SINGLE (TRUSTED) SYSTEM!!