Now I wont be the first to mention this and certainly not the last, but as someone who actually does get out of the office on most days, I can personally recommend this!
I regularly jog first thing in the morning and recognise the benefits not only from the fitness and health perspective, but also from the 'me time' I get whilst there are no other distractions - other than traffic! This allows me to either concentrate on work things, family things or even no things without interruption! I also get back have a shower and feel refreshed ready to get into the days work ahead.
Now first thing in the morning may not be 'you' or, due to travel etc, it's just not practical which leads me to the 2nd 'get out of the office' - go out for at least 20 minutes sometime during the day. Ideally lunchtime but when your schedule can fit it in. And talking of schedule, if you can schedule a meeting with clients, you can certainly schedule a meeting with yourself so put it in your daily diary/calendar! When it's in there you are more likely to adhere to it. Taking 20 minutes (at least) out of the office, away from email, away from the phone (leave your mobile at the office unless it is essential you carry it with you ie for Safety/emergency not 'in case a client calls'), and go for a walk, jog, swim, cycle or whatever. Something that allows you to assess the day so far, assess the day ahead and address any items that need addressing. Make a plan then instigate it when you get back to the office.
Go forth and realise your dreams and make sure you try to get out of your office to meet with yourself, daily!