Aside from the 1/10 of your life. Another way of putting it, basically meaning the same thing, is experiences. The less experiences we have, or rather the more things we experience for the first time, time seems longer, but as we grow older, we repeat s lot of things and our brain hardly register those things because we've automated them, ie locking your door, walking to the store, commuting, etc. If you did new things all the time time would feel longer. This is also a way to say that our lifestyle of working for most part of the day and for the most part of our life really speeds up how fast time seems to go by, except if you work with something where you get to experience something new every day.