Activity is the leading cause behind success. In today's environment, it can be very easy to rely on outside forces to determine your success.
"Nobodies calling me back!"
"The phones aren't ringing!"
"I'm not getting any deals!"
The exterior person woudl begin creating excuses (see above) about why those things are happening. It's the economy... it's the time of year..., nobody buys anything right now..., etc.
On the other hand, an interior person begins to think of activities they can do to solve their problem. Now they have control! By focusing on things you can control (i.e. more phone calls, more text messages, more emails) these things begin to build their success.
Be an interior thinker! It is the easiest way to success!