Humans have three “parts” - soul, ego, body.
The soul is the part which is truly “you”. It is the universal energy. The aim of yoga is to reach this part.
Nature of the human soul: love, equality, peace, joy Nature of the human ego: desire, duality, judgement
Meditation is a method to reduce the ego. By reducing the ego, we reach our soul.
It can be said that yoga really means Samadhi (the 8th limb of Ashtanga), which is self-realisation (becoming just the soul).
A permanent state of Samadhi will result in you no longer being human, as a human requires the ego. Examples are Buddha and other spiritual figures. It is also possible to have temporary Samadhi, where the ego goes for a while but returns. The human will return with knowledge acquired from being connected to the universal energy, e.g. Patanjali gained knowledge about yoga.
Yoga introduces steps to help us meditate and to therefore reach Samadhi. These include the final limbs of Ashtanga:
There are many yogic techniques for concentration.
So, the steps are:
Happiness
There is a difference between joy and happiness. Whereas joy is the nature of the soul and is intrinsic, happiness is getting what you desire. It is an emotion linked to the ego. On the flip side, suffering is the absence of getting what you desire.
Happiness is not the aim. If something makes you happy, you will have a fear of losing it. Even when happy, there is not 100% satisfaction.