On a serious note (if applicable), there is no "bad" or "good" qi/jin. Just good, and bad intent. Killing someone who is a threat is not per se evil, just a short route. If you would be talking of the essence of feeling, of course you can "harness" bad feelings, building lots of hate. I somehow doubt it would be helpful, on the long sight. You can harness good feelings, and still keep capable of going into fight mode if necessary. The difference would be to keep fighting as long as necessary, and having other emotions opening other solutions.

BTW, "good" intentions do not always overcome bad ones. It could happen to you that your intentions don't stop the bad guy from keeping bad. Bad force is the same as good, just force. Someone who is in contact with his soul, however you call it, would on the other hand if reasonable strong usually find ways of outsmarting the other guy. Out of my guts I doubt that too often, people are enough in contact with themselves to fall in that category. However, you can try, and see what happens. As long as you do not "decide" there is magic before you experience what you can do, and what you cannot, you can take that journey, learning what it can offer. But, usually your concern should be to have the right sort of "friends", the right location to live in, a reasonable job, education, family, etc. That would address most of the trouble you really come by.

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"Fawning, but proud!" - (at least sometimes, in rare cases)
"Killing them all didn't make it any better..." - "Are you a freak or something ???" - Max Payne
"Theft is a crime, even in Iraq." - Me.