This is taken from a colleagues post elsewhere:
One of my mentors paraphrases Siva Sutra 3.13 this way: “A Siddha lives in total freedom.”
My mentor comments further: The state of a Siddha is the state of freedom.
For the embodied soul there are only two possibilities. One is the state of bondage in which he loses the awareness of his nature, his glory, his power of understanding, and becomes contracted. He feels, “I am small, I am a sinner, I am subject to birth and death.” His own outlook is the thing that shrinks him day by day. As he meditates on and ponders his own limitations, he becomes completely bound.
The other possibility is the state of absolute freedom. By the grace of the Guru, a person’s inner Sakti is awakened through the process of shaktipat. Unfolding, his Sakti fills him with consciousness, and he is gradually freed from cravings and desires, the pull of the sense organs, and from all limited states. He achieves total union with the supreme Self.
A person who has achieved mastery over his senses and their objects is called a Siddha. One who sees this world, which the ignorant experience as full of sorrow, to be the outer sport of Parasakti is a Siddha. One who has risen above the three bodies and their corresponding states is a Siddha. One who has rid himself of notions of acceptance and rejection and has burned away the imaginary distinctions of virtue and sin, enjoyment and liberation, worldliness and spirituality in the fire of inner knowledge is a Siddha. That great soul regards all the thoughts that arise within him, whether good or bad, as the stirrings of the Self. One who has become the universe, the Lord of the universe, and the Soul of the universe; one who is his own path and his own destination; one who is fully active and yet supremely inactive; one who is aware “I am Siva” – he is a Siddha.
So ends the commentary.