Addiction is any compulsive, habitual behavior that limits the freedom of human desire. It is caused by the attachment, or nailing, of desire to specific objects. The word behavior is especially important in this definition, for it indicates that action is essential to addiction.
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There is a vast difference between doing these things because we freely choose and doing them because we are compelled. In the first case, the motivation is love; in the second slavery.
From Addiction and Grace: Love and Spirituality in the Healing of Addictions