Sometimes it is doubt in your own ability which holds you back most of all...
In Buddhist meditation, the "Five Hindrances" can be seen as the major forces in the mind that hinder our ability to see clearly or become concentrated. They are universal, we all experience them. These hindrances are represented by Maara the tempter who comes to Buddha whilst he is meditating for enlightenment. Doubt is thought to be the most dangerous of the five hindrances as it is the one which can cause a person to give up their practice.
We may have doubt in our ability to practice or doubt in the teachings themselves. Doubt prevents us from fully applying ourselves. Although these are taught as hindrances to meditation I found that they really rung true for my yoga practice too. If I don't manage to make it out to the mat when I intend to it is usually doubt which seals my decision- Am I strong enough today? Am I going to benefit today? Do I benefit at all?
When I'm in a positive mood I am able to push these thoughts aside, get to yoga and let my body give me the answers. However, when you're not feeling great, doubt can really push you under. I find that the best remedy for overcoming this is trying to be mindful, having a mindful, present practice, letting yourself melt into the poses without thinking about what you can and cannot do.So, next time when you're questioning your practice (or yourself!) try taking it one step at a time, focusing on the process, not the outcomes.