The joy we get from singing bhajans and by performing worship is temporary. But by experiencing the essence of "soham" mantra, you will get eternal joy. This soham is also known by the name "Hamsa Gayatri". "So" means "that"; "ham" means "I am". "I am that" is the meaning of soham. You should chant soham with every breath. When you breathe, you are inhaling "so" and you are exhaling "ham". If we repeat soham mantra with every inhalation and exhalation of breath, it will do a lot of good to you. Repeat "soham" with every breath and watch your breath carefully.