I have already spoken about it in the Patanjali Yoga Sutras.
Vyadhi, Styana, Samsaya, Pramada, Alasya, Avirati, Bhranti Darsana, Alabdha bhumikatva and Anavasthitattva. These are the nine obstacles.
Physical disease, mental inertia, doubts coming to your mind about the path; and then not attaining any state, not having any interest in anything.
These are all momentary obstacles that come to any yogi. But when you continue with one pointed devotion you can overcome all these obstacles.
It is not a big deal, they come and they go.
Many of you have had this problem, sometimes you don’t feel like meditating and afterwards suddenly your meditation became deep. Or sometimes so many doubts come to your mind and then suddenly one day they all disappeared.