It is important to make sure that you put cushion time in your schedule. While thinking about what to write to expand on this topic we came across one of the definitions of cushion that is interesting and relevant.
Cushion (noun): something helpful; something that limits the effect of an unpleasant situation.
That is exactly what cushion time does; it limits the effect of something unpleasant like your client being late or getting stuck in traffic.
Cushion time can be as simple as leaving enough time between meetings to make sure you arrive on time. I used to be notorious for scheduling a hour long session with a personal training client at 8am and scheduling a nutrition client across town at 9am. It looked fine in my schedule but logistically would not work.
Even if you don't have to travel, cushion time between appointments can help give you a break and/or breathing room if a client or customer is early or late.
How about if it is a new place you are going to? Leave extra time to get there and figure out where you need to be. What if you have to go around the block a few times to find parking... will that make you late? Or did you leave enough "cushion?"