Do I have to practice all of the principles of yoga to benefit from it?

Not necessarily. Each principle has the potential to lead a person toward harmony in self and society. Rules for living in society and self-restraining rules help in regulating the functioning of the human being, giving balance in life. Low physical impact postures (asana) and relaxation help in removing the stress in the mind and strain in the body, thereby augmenting balance within and with environment. Breathing techniques help in improving oxygen flow and giving balance in life. Detachment of the mind from the senses, concentration, meditation, and complete union with a super consciousness are also called inner yoga and help in restoring balance of mind with surroundings. The ultimate purpose of yoga is balance that leads to self realization.