Chapter 6 Dhyana Yoga Verse 9
Yuktaahaaravihaarasya yuktacheshtasya karmasu;
Yuktaswapnaavabodhasya yogo bhavati duhkhahaa.
Yoga becomes the destroyer of pain for him who is always moderate in eating and recreation,
who is moderate in exertion in actions, who is moderate in sleep and wakefulness.
In this sloka Lord Krishna talks about what a person who does all his things moderately will achieve. The first point Lord Krishna makes here is that Yoga is a tool that destroys the pain. But it is not applicable to everyone. It is a pain destroyer for that person who is moderate in his eating habits and recreation. Recreation here talks about the enjoyment. Lord Krishna also says that yoga is a pain destroyer for someone who is moderate in exerting his actions and also the one who sleeps neither less or more and the person who remains awake moderately.
Extending Interpretation to Mankind’s Life!
The point that we have to understand here is what is the pain that Lord Krishna says will go from doing yoga in the form of meditation. First one should understand that mediation is the higher form of yoga. A person will start his Yoga by doing asanas that are meant to keep his body fit. A fit body automatically leads him to fit mind. For the mind to remain fit he progresses from asanas  towards meditation. The pain that Lord Krishna is referring to is the pain that the soul feels. Can a soul feel the pain? If so what is that pain?
If you fall down and get hurt your body will feel the pain of it because body is linked to senses and you can only see anything that is connected to senses. But if you fall down spiritually or doesn’t go up with the speed with which you should go up, then your soul will also feel the pain. But since soul is not connected to any sense organs, you will not feel the pain. Just because you are not feeling the pain, it doesn’t mean that the pain doesn’t exist. The pain that a soul feel is more long lasting than that of body, because treatment removes body pains but what will remove the pain of the soul?
The pain of the soul can be removed only when a person takes the spiritual path. How many times you felt bad that you are not doing things that you are supposed to do? This feeling of “feeling bad” is nothing but the pain that your soul is feeling. It always wants to go in the quest of Brahman and if we dont take that path it feels the pain. That pain can be removed by doing meditation because, when you meditate it will start the journey of Atman towards Brahman and which is what every Atman desires and aspires for!