Sannyaasa is the renunciation of life and action and of the threefold modes of Nature, but it has to be approached through one or other of the three qualities.
The impulse may be tamasic, a feeling of impotence, fear, aversion, disgust, horror of the world and life; or it may be the rajasic quality tending towards tamas, an impulse of weariness of the struggle, grief, disappointment, refusal to accept any longer this vain turmoil of activity with its pains and its eternal discontent. Or the impulse may be that of rajas tending towards sattwa, the impulse to arrive at something superior to anything life can give, to conquer a higher state, to trample down life itself under the feet of an inner strength which seeks to break all bonds and transcend all limits.
Or it may be sattwic, an intellectual perception of the vanity of life and the absence of any real goal or justification for this ever-cycling world-existence or else a spiritual perception of the Timeless, the Infinite, the Silent, the nameless and formless Peace beyond.
Ref: Essays on the Gita