Breathing exercises can help unlock some of the places that are blocking your progress. Emotional energy can be held in your body and released with breathing exercises. Freedom from habits can be minimized.
Altered states of consciousness easily accessed.
Is mantra a expression of worship or some religion? No, it is a method used to signal the brain with new neural messages thus changing our brain function in a more positive direction.
Kriyas are a set of exercises in a particular order to create a specific effect. Kundalini has 1000's of Kriyas producing positive effects and balancing the chakras.