Swastha is an Ayurvedic term for health. It means "to be founded in the self" The self stands for the deepest inner level of being. In yogic philosophy we say atman. It is the indestructible, eternal essence of the mind. The self is the level of human life that gives the healthy person a feeling of identity and inner wholeness, it remains unaffected by illness, disharmony and tension. Everyone is integrated into the unity of nature and the cosmos.
Through stress, hectic life, high demands, a lot of pressure you lose the connection, the connection to your own self. Those who have lost this connection tend to harm themselves, to ignore their own needs and to ignore the inner voice of the heart.
This loss gives rise to fears, depression, problems and illnesses. Yoga shows a way how one can free oneself from this negativity.