I'm responding to Jugu's original message. This is just speculation based loosely on my experience.
When I meditated as a youngster (early 20s), my experience was similar to Jugu's. I was already an introverted personality, and after intensive meditation I became very introverted and depressed. All I wanted to do was meditate all the time, or lie around and watch the world go by. I did not know God at that time and didn't have much of a value system to guide me.
After leaving meditation, I found God and have lived my entire adult life as a devout believer in Christ. From my faith I learned about love of God, humility, morals, and compassion. Much of the time I was not fully able to live my beliefs, but they were nevertheless pretty thoroughly ingrained in my personality as important values.
Last year I returned to meditation within the context of my Christian faith, and my experience has been completely different. Meditation has brought tremendous peace, a sense of oneness with God, less ego, and a lot more compassion. It's enabling me to better live all those values I learned. Life is almost all joy.
What caused the difference between the two experiences (a gap of 25 years)? I really don't know, but having lived a while now, I find compassion comes more naturally because I know something about the suffering life brings first hand. For some reason, meditation has intensified compassion. Knowing God may be a factor also. With God there is meaning even as dualistic belief fades. I said elsewhere in this forum that it feels like I am slowly disappearing and God is more fully present. It is a joyous experience, and I am much more comfortable with life and society, much more accepting of whatever is.
The last possible factor is that I learned a certain amount of extroversion over that 25-year period. I'm not the shy introverted kid I once was. Meditation no longer intensifies my introversion, perhaps, because I am no longer an introvert (though I am not quite a true extrovert either).
I wonder about this: If someone starts out without God and without a love of people and of life in general, as the ego diminishes through meditation, perhaps only an introverted nothingness remains, leading to nihilism, existential crisis, and a distaste for society.
On the practical level, if someone has such an experience, it seems like just stopping the meditation for a while would solve a lot of the problem. The other answer may be to enhance one's love of God and people, perhaps by finding a group of people to hang with who practice those values. It might all seem like an empty game at first, but time might change things. After gaining some maturity, it's possible a return to meditation might bring a new, positive form of non-dualistic awareness, as it did for me.
Charles (or RC as Andy calls me