Utsāha is an essential factor in matters governing human thoughts and actions, and directs all human achievements because primarily it is the strength of will, firmness of resolve, energy and power, endurance and perseverance, and the joy and elation resulting from achievement of pre-determined objectives.
Utsāha (Sanskrit: उत्साह) means – 'enthusiasm', 'zeal', 'energy', 'strength', 'power', 'fortitude', 'strength of will', 'resolution', 'firmness', 'effort', 'endurance', 'perseverance', cheerfulness', 'joy', 'happiness'; it also means 'initiative' or 'drive'.
Sridharswami regards joy as the energy (utsāha) of the mind due to the attainment of cherished objects or the union with a beloved person; in other words, utsāha is a mode of essence of the mind; it is an essential psychical element in a violation, which precedes a voluntary action. Therefore, Madhusūdana describes it as a resolution of the mind.Utsāha or enthusiasm is roused in superior persons by the absence of sadness; this dominant state rouses the vira rasa or the emotion of heroism, and by rousing utsāha, jadata or stupor and nidra or sleep caused by physiological action, is inhibited.
Bharata, the legendary author of Natyashastra, speaks about the nine primary emotions by which Rasa, the primary sentiment that appeals to poetic sensibility, is nourished; they are – rati ('enjoyment'), hāsya ('mirth'), śoka ('grief'), krodha ('anger'), utsāha ('enthusiasm'), bhaya ('fear'), jugupsa ('disgust'), vismaya ('surprise') and sama or śanta ('peace'), based respectively on nine navarasas ('primary sentiments').Utsāha or energy relates to persons of the superior types, and this sentiment is caused by Determinants such as absence of sadness, power, patience, heroism and the like, and is represented on the stage by Consequents such as steadiness, munificence, boldness of an undertaking and the like.
According to Abhinavagupta the rasas are like gods, and śanta is like their highest centre, Shiva, he insists on transcendence as the highest value in literary aesthetics. Bharata does not consider complete detachment, Nirveda (world-weariness) as the sthāyibhāva of śanta because detachment ordinarily does not arise from knowledge of the truth. Ishvarakrishna states that from detachment comes only prākrtilaya i.e. the dissolution of the eight causes, and not moksha, and Patanjali states that from knowledge of truth arises aversion to the gunas (detachment) which is really the highest state (kaśtha) of knowledge. Atman alone, possessed of pure qualities such as knowledge, bliss etc., and devoid of enjoyment of imagined sense-objects, is the sthāyibhāva of śanta. Śanta is sama and sama is the true nature of the Self. Energy may be said to be based on egoism as its essence, and śanta may be said to consist in the loosening of egoism, but there is no state that is devoid of utsāha (energy).Utsāha or dynamic energy is the sthāyibhāva or primary state of vira rasa, without utsāha one cannot act; Nātya Śastra VI.66 tells us that vira rasa is a dynamic energy (utsāha) which arises from various causal factors (arthaśeśa) such as decisiveness, not giving way to depression, not being surprised or confused.