What's something that if you think about it for too long it freaks you out?

I 100% agree. It just seems that as we age, we get more comfortable in similar day to day activities. Those activities do not stimulate the formation of new dendritic connections like novel activities, so we perceive that time as passing by faster. In fact, the perception of time is more a high level manifestation of our brain's physical mechanisms for storing information as memories. Less memory formation, the quicker time is perceived to pass.

Obviously that is on a chronic time scale. Acutely, time passes faster when we are enjoying ourselves, and slower when we want it to pass faster. That is just a perspective issue. It's very interesting to think about!