Within oneself is peace to be found, not from another will a bhikkhu find peace. For one who is inwardly calmed, nothing is accumulated, how then rejected?
Just as in the centre of the ocean no waves arise, but all is still; so, steadfast and free of lust, on what is there for a bhikkhu to build arrogance? (Sutta Nipāta 919-920)
Spiritual peace is a subjective experience rather than an external reality. It is found by looking within oneself through the development of internalized meditation practices.
The development of Calm Meditation (samatha kammathāna) through the use of various concentration exercises can produce a strong temporary feeling of inner quiet. When the mind can be collected upon a meditation object such as the sensation of natural breathing at the nostrils, wandering thoughts are calmed and mental noise is silenced. That mental noise or internal dialogue is mostly obsessive self-reference through either affirmation or denial. The silencing of mental noise is the silencing of this self-reference, with its disturbing pride and desire.
Calm Meditation, however, only provides a temporary experience of quiet. It is through the development of Insight Meditation (vipassanā kammathāna), with an emphasis upon penetrating investigative awareness, that we are able to see the true nature of things clearly, and free ourselves from the very structures and sources of disturbing self-reference.
Inner quiet then becomes as stable and natural as the waveless depths of the sea.
This reflection by Ajahn Thiradhammo is from the book, Treasures of the Buddha’s Teaching, (pdf) pp. 77-78.