Destiny or Karma

Karma: n.
The total effect of a person's actions and conduct during the successive phases of the person's existence, regarded as determining the person's destiny.
Fate; destiny.
A distinctive aura, atmosphere, or feeling
Destiny: n.
The inevitable or necessary fate to which a particular person or thing is destined
A predetermined course of events considered as something beyond human power or control
The power or agency thought to predetermine events
I'm not sure if I believe in Karma or not. I used to, seemingly only when something bad happened though. Why is it we believe in a concept of Karma when it's a negative situation but believe in Destiny when it's a positive situation?

By definition destiny determines karma it seems.

I'm the first to admit that when something crappy happens to me, I've been wronged or heard of someone wronged I state "what goes around comes around" and although this is rather petty it is easier to place blame on another to say it's their crappy karma then to admit it might just have been my destiny for it happening.

I've been thinking about this concept a lot lately and I have experienced through observation the 'what goes around' concept to others and find it no more fulfilling when something bad happens to them then when it happened to me. So this leaves me with what about if you don't want to believe it's a 'what goes around' concept? Cause then you get to thinking…is wishing bad karma upon them going to come around to you too?

How do you explain it when a person has followed the rules? When they have loved properly? They have done their best to be kind? How is it their "Destiny" or "Karma" to be sick, heartbroken, battling demons they didn't "ask" for?

Does a Destiny or Karma truly determine who you are as a person? Does it measure your mental strength or your ability to stand tall even when a present concept is crushing you?

I find I have an undeniable strength of self. I always have. Is that a Destiny?

Does one's Destiny have a cause in another's?

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"1 So I reflected on all this and concluded that the righteous and the wise and what they do are in God's hands, but no one knows whether love or hate awaits them. 2 All share a common destiny—the righteous and the wicked, the good and the bad, the clean and the unclean, those who offer sacrifices and those who do not." Ecclesiastes 9
"I can't control my destiny, I trust my soul, my only goal is to just be." - Jonathan Larson
Maybe that's all it takes.