I think the most difficult part of the meditation experience is the seizing up of time. The seizing up of time proves that time is an illusion. Yet, it takes the body and mind time to process this. The body and mind are very structured and conditioned in time. When we touch the "eternal present" time has this effect of seizing up and body and mind have a tendency to resist losing the structure of time for some time. After a while, it will eventually even out in the middle between time and the present moment. Yet, it can be a difficult process for the body and mind to handle initially. This is why to allow yourself simple surrender is a good discipline in meditation.