Pratyahara is withdrawal of the senses. The breath is an extremely useful tool for this and asana helps to get the body ready for stillness. Building on the prior four limbs of yoga, pratyahara brings the meditation deeper, into a deeper compression and concentration. The senses become more potent and still they must be brought under the control of the breath. The fifth limb of yoga allows for great peace and release from the illusions of the primary senses of hearing and vision. It deepens feeling.
Meditation is most potent when single-minded and focused on a single thing and practicing pratyahara helps to make this more potent. It brings appreciation for the ability to perceive and experience the world in the gift of your body. It builds Santosa and strengthens the other roots, and deepens all the way into the eighth limb of yoga, Samadhi.
Science helps to understand that the senses are constructive, they actively create what we know as consciousness. Everything seems brighter, newer, and fresh after sleep, so pratyahara helps to reinforce his, again creating appreciation for the experiences of everyday life. It is also important to understand that the good experiences in life are all a perspective that you have decided upon. Then one can try to see both for their lessons and choose to avoid attaching feelings to either one. It is an important aspect of yoga to view the senses as part of attachment to the outside world and that all attachment is fleeting.
But withdrawal is only as important as its balancing counterpart, service and communion with others. It is surely true that community plays a role in the happiness of an individual and that complete withdrawal is not necessarily the way to live the happiest life. Balance in all things is necessary, especially with withdrawal from the surrounding world. But the idea is that by detaching, you will open your eyes and ears to a new world of wonder with appreciate and gratitude for all that is, every detail, every minutiae. And after withdrawal, the single pointed focus of Dharana is obtained, the following limb of yoga.
Patanjali’s limbs are a system, meant to scale the heights of knowledge of the self or Raja yoga. After mastering prana-yama, sense withdrawal becomes the focus of a practice, leading to single pointed focused concentration, Dharana, the 6th limb of yoga.