The conditions of this joy, increasing and decreasing, coming and going, they all depend on the mind. The enlightened one does not think that the existence of the body is my existence. Death is nothing to me, the enlightened one says. This is the enlightened one's attitude towards joy. Aham Brahm Hasmi, Aham Anandoh, I am bliss in that sense. Now that bliss, just as worldly pleasure, other worldly pleasure, can be expressed and measured, but Anand itself cannot be expressed or measured. That's why it is two words that are used here: Anir Desham Paramam Sukham, Sukham Happiness.
Swami Sarvapriyananda teaches the Katha Upanishad, one of India's most revered texts which is also a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).