Learn How to Breathe...

Breathing is the key to yoga.

Its what brings the asanas to life and gives yoga its flow. The idea is to keep your awareness on your breath continuously as you move in and out of each pose. And depending on whether you want to relax, balance, energize, you can vary your breathing pattern to get the desired effect.

Different kinds of breathing can enhance your yoga practice

Lengthening and then holding your exhalation after all the air is expelled relaxes you, while lengthening and holding your inhalation increases your energy. Be careful though, if you are feeling stressed, you are better off using a balanced breath pattern as holding your inhalation can make you more tense.
The breath ratios at the top of below chart are very relaxing, while those at the bottom are energizing. If you pay careful attention and adjust your breathing accordingly, you can both relax and energize yourself at the same time.

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4 (Inhale) 1 (Hold) 8 (Exhale) 4 (Hold) Relaxing
4 (Inhale) 1 (Hold) 12 (Exhale) 1 (Hold) Relaxing
6 (Inhale) 1 (Hold) 10 (Exhale) 1 (Hold) Relaxing
6 (Inhale) 1 (Hold) 8 (Exhale) 4 (Hold) Relaxing
8 (Inhale) 1 (Hold) 8 (Exhale) 1 (Hold) Balanced
6 (Inhale) 2 (Hold) 6 (Exhale) 2 (Hold) Balanced
6 (Inhale) 4 (Hold) 6 (Exhale) 1 (Hold) Energizing
6 (Inhale) 6 (Hold) 6 (Exhale) 1 (Hold) Energizing
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In the above first example, inhale for 4 counts, hold for 1, exhale for 8 counts and hold for 4. Your counts may be faster or slower depending on your lung capacity