Upon being established in sexual continence, vigor is gained.
The ordinary interpretation of Brahmacharya is sexual continence. Yoga looks at conserving sexual energy which Nature has gifted us for procreation: the propagation of the specie and the advent of the embodiment of a Spirit Soul to experience tangible transcendence (or TANgible TRAnscendence which is a very apt definition of TAN-TRA). According to Yoga this primal urge left unchecked results in a loss of vigor as each release of sexual energy is an act of sacrifice on behalf of the participants—we release our genetic material in a concentrated medium under tremendous force in order to fertilize a womb. The release of this sexual force also implies a downward flow, from Spirit to Matter and hence from a more rarefied state to a denser state. On the other hand, when our sexual force is reversed by the uplifting of our consciousness from Matter to Spirit, it rises up the Chakra system to the 1,000 Petal Lotus, the Seat of Higher Consciousness where MA Kundalini (Shakti) can embrace Consciousness (Shiva) Itself. From this we can see / deduce that our sexual energy is actually our potential Kundalini energy (Causal) ‘liquefied’ (Astral) to become our sexual fluids (Physical) for material procreation. On the other hand, our sexual fluids (Physical) can be alchemically transmuted (rarefied—Astral) to become Spirit Essence (Causal) for spiritual and mental procreation which is the very reversal of our sexual energy (in and up instead of down and out!).
This leads to the true interpretation of Brahmacharya. Dissecting the root of the word we obtain: Brahma (God) and charya (action). Hence Brahmacharya is God or Divine action.
When we consciously perform acts of material, spiritual or mental procreation, we are performing Divine actions, a Holy Act. When it is done unconsciously and without a sense of the sacred, then it is an act driven blindly by the forces of material nature and by the ego (power, status, frustration, addiction etc…).
Whether we perceive the Sexual Force as an expression of the God/dess Force is dependent on our attitude towards the Sacredness of the Expression Itself. So Tantra states: Be the Attitude (Be-Attitude or Beatitude, recognizing the Sacred in all beings, all things and all acts).
True continence is not in suppression or repression but in transmutation which starts with true understanding of the Sexual Force as the God/dess Force Itself. If that understanding is applied with a sense feeling of deep devotion towards its expression then vigor is gained instead of a sense of loss in vitality.
Whatever form the sexual impulse may take, know that it is the Divine Energy coursing through you. Honor it as such!