A definition of transmutation by Roberto Assagioli from his book Psychosynthesis.
Once the choice of the ideal form has been made, practical psychosynthesis, the actual construction of the new personality, begins. This work may be divided into three principal parts:
Utilization of the available energies. These are (a) the forces released, by the analysis and disintegration of the unconscious complexes; (b) the tendencies latent, and until now neglected, which exist on the various psychological levels. Such utilization demands the transmutation of many of these unconscious forces. Their inherent plasticity and mutability makes this possible. In fact, such transmutation is a process that is continually taking place within us. Just as heat is changed into motion and electric energy, and vice versa, our emotions and impulses are transformed into physical actions or into imaginative and intellectual activities. Conversely, ideas stir up emotions or are transformed into plans and hence into actions.
Instances of such transformations have been observed and recognized by many people. When the Latin poet says, “Facit indignatio versus” (Indignation produces my poems) he shows that he has realized how an emotional wave of indignation, if denied a natural outlet through external action, can be transformed into poetic activity. Again, when Heine writes, Aus meinen grossen Schmerzen much’ ich die kleinen Lieder (Out of my great suffering I produce my little songs) he indicates that his pain has been sublimated into poetry, and thus transfigured into beauty.
Important teachings and examples concerning the doctrine and practice of this transformation of the inner energies can be found in the yoga of the Hindu, in Christian mysticism and asceticism and in works on spiritual alchemy, while some points have been contributed by psychoanalysis. We, therefore, possess sufficient elements for the formation of a science of psychological energies (psychodynamics), and of reliable and adequate techniques by which to bring about the desired changes in ourselves and in others. Read also his article: Transmutation and Sublimation of Sexual Energies