Your sense of the present is based on your relative situation compared to your past situation. The totality of the situations stored in memory with enough resolution and 'present-ness' to make this comparison can only extend so far back into the past. (a few hours)
When you do any activity long enough that the entierty of your comparative memory is that same activity, you lose that relative sense of time and enter the state of timelessness and connection to the entire universe, discreteness stops existing, the self stops existing, because there is no point of reference for you to compare anything to in your memory of immediate experience.
