Cleanliness and purity of body and mind, an attitude of contentment, training of the senses, self-study and reflection on sacred words, and an attitude of letting go into one's source are the observances or practices of self-training are the second limb of the 8-limb path.
The five Niyamas: The five Niyamas are the observances or practices of self-training, and deal with our personal, inner world.
Reference from swamij.com
Training body, mind, and senses
Having a healthy body, clear mind, and regulated senses is necessary if we wish to sit for meditation and experience the depths of Self-realization. The five Niyamas are a means for self-training in relation to body, senses, and mind.
Actions, speech, and thoughts
It is easy to mistakenly lump these three together, as if they are one concept. Most of our human experience does not teach us how to separate, or contemplate these parts of the mind. These three separate practices, which work together intimately, to cultivate self-awareness or mindfulness of actions, speech, and thoughts as separate entities is very important. Witness your actions, speech and thoughts as an independent practice, though related to the others.
At the same time that one is aware of actions in the external world through practicing the Yamas, he or she also becomes aware of the personal, inner processes related to body, senses, and mind, by practice awareness of the Niyamas. By mindfulness and self-awareness, you see when your actions are contrary to the Niyamas (as well as the Yamas), and you can counter that by noting that the action is not useful, and acting more in line with the Niyamas.
Through similar mindfulness and self-awareness of speech in relation to the Niyamas, you see when your speech is contrary to the Niyamas. This can also be countered that by noting that the speech is not useful and speaking more in line with the goals of the Niyamas.
The subtlest level of self-awareness and self-regulation is that of thought in the inner world. Each of the Niyamas are consciously practiced at the level of thought. By mindfulness and self-awareness, you see when your thoughts are contrary to the Niyamas, and you can counter that by noting that the thought is not useful and promoting positive thoughts that are more in line with the Niyamas.
Coloring or klishta
What is ultimately most important is the coloring or klishta, the qualities of the subtle mental traces, or samskaras in the karmashaya. These form the veil, that blocks the direct experience of the center of consciousness. It is not that "I am" an impure body, cluttered mind, or a sensory addict, etc. Rather, it is the thought patterns deep in the basement of the mind (chitta), which have been colored in some way, which in turn affect the body, mental processing, and the sensory attractions and aversions.
Niyamas and Life
You are probably already practicing many of these observances, but continuing to cultivate your awareness to them is essential.
Meaning of Ishvara:
In the Upanishads, the word Īśvara is used to denote a state of collective consciousness. Thus, God is not a being that sits on a high pedestal beyond the sun, moon, and stars; God is actually the state of Ultimate Reality. But due to the lack of direct experience, God has been personified and given various names and forms by religions throughout the ages. When one expands one's individual consciousness to the Universal Consciousness, it is called Self-realization, for the individual self has realized the unity of diversity, the very underlying principle, or Universal Self, beneath all forms and names. The great sages of the Upanishads avoid the confusions related to conceptions of God and encourage students to be honest and sincere in their quests for Self-realization. Upanishadic philosophy provides various methods for unfolding higher levels of truth and helps students to be able to unravel the mysteries of the individual and the universe.