The navel is the central seat of the Vital, the Life Principle.

If you want to change, you must first resolutely get rid of the defects of your vital being, persevering steadily, however difficult it may be or however long it may take, calling in always the divine help and compelling yourself always to be entirely sincere.
As for the fitness and unfitness, nobody is entirely fit for the yoga; one has to become fit by aspiration, by abhyasa, (practice) by sincerity and surrender. If you have always desired the spiritual life, it is the psychic part of you that desired it, but your vital has always come in the way. Establish a sincere will in the vital, do not allow personal desires and demands and selfishness and falsehood to mix in your sadhana; then alone the vital in you will become fit for the sadhana.

It is when the vital gets broken up, some strong movements of it, desires, greeds, may precipitate themselves into animal forms, e.g., sexual desire with the part of the vital consciousness under its control into a dog or some habitual movement of excessive greed may carry part of the vital consciousness into a pig. The animal represents the vital consciousness with mind involved in the vital, so that it is naturally there that such things would gravitate for satisfaction.