The reasons why being still in meditation can be challenging, is because of one (or more) of five things: sensual craving, ill-will, slothfulness, restlessness and doubt. Ajahn Nyanadhammo explains what the Five Hindrances are and how to overcome them to attain tranquility and insight.
Teachings are available for downloading from the BSWA Youtube Channel, the BSWA Podcast, and Deeper Dhamma Podcast.