The mind is the self - they are one and the same.
When you help someone (your example) and you feel freedom/joy as a result, it's because your mind will be silenced by the process. Any action which approximates love will have the same effect on the mind.
Given what you've said here, you probably won't like the book I recommended. But at its core, it is the same as Christian mysticism.
You know the darkness you feel when you start to let go of the mind? The darkness is the way the ego tricks you into avoiding falling into the Absolute (or what Christians would call God).
I'm not Christian, but I like to look at spirituality from multiple viewpoints. Bernadette Roberts was a Christian nun. If you're serious, you will be able to make sense of her work linked here, then match it with your personal experience of impending darkness and what I'm saying here. http://www.nonduality.com/berna.htm
Chapter 1 - "Roberts describes a quality of silence she had known on occasions, which was so total as to evoke fear, annihilation, point of no return".
I can partly agree with you about the mind getting silenced. But I would explain it differently. If I do something good for someone else right now, and it's inconvenient for me , it's somewhat of a blow to the 'flesh' , but also tends to make one feel more ordered within. However there is certainly more to it than just trying to be a good person or following rules. These things alone might be drudgery for a person. “Peace I leave with you; my peace I give to you. Not as the world gives do I give to you. ” (Christ). So to the Christians it is something divine as well, and better than what the world can offer.