Before we look at the essence of this, the last of the niyamas, let’s just deal with the ‘God’ word. Yoga does not promote any religion. There is no requirement to believe in God, or gods (Hindus have thousands). Yoga does however acknowledge that there is some kind of profound concept beyond our immediate reality.
The word Isvara is most commonly translated as God. But the meaning is simply something bigger than ourselves: a higher power or higher self; divine or universal energy, collective consciousness or nature.
Leaving aside Isvara, I think that it’s Pranidhara that is the essence of this niyama, of yoga and of life itself. It can be translated as surrender, or devotion or more broadly as letting go, opening, accepting. In yoga we can practice surrendering in the flow of a sun salutation, accepting where we are in each asana and letting go of the ego involved in wanting to be better.
Off the mat, surrendering, letting go and accepting is not to say that we just give up and make no effort. It is more that we do our best but let go of expectations, of attachment to the outcome. We can see all our actions as a practice of devotion – to a higher power, to our true self or to humanity as a whole.