What’s exact reason that if I do bad to others, bad will happen to me?
Righteousness.
The heart is more deceitful than all else
And is desperately sick;
Who can know it?
I, Am who Am, search the heart;
I test the inmost being,
Even to give to each man according to his ways,
According to the fruit of his deeds.
Jeremiah 17:9-10
Do not be deceived, God is not mocked, for whatever a man sows, this he will also reap. For the one who sows into flesh of self will from the flesh reap corruption, but the one who sows into the Spirit will from the Spirit reap life eonian.
And let us not be weary in
well doing: for in due season
we shall reap, if we faint not.
Galatians 6:7-9
MN 115 :
They understand: ‘It’s impossible for a likable, desirable, agreeable result to come from bad conduct of body, speech, and mind. But it is possible for an unlikable, undesirable, disagreeable result to come from bad conduct of body, speech, and mind.’
They understand: ‘It’s impossible for an unlikable, undesirable, disagreeable result to come from good conduct of body, speech, and mind. But it is possible for a likable, desirable, agreeable result to come from good conduct of body, speech, and mind.’
They understand: ‘It’s impossible that someone who has engaged in bad conduct of body, speech, and mind, could for that reason alone, when their body breaks up, after death, be reborn in a good place, a heavenly realm. But it is possible that someone who has engaged in bad conduct of body, speech, and mind could, for that reason alone, when their body breaks up, after death, be reborn in a place of loss, a bad place, the underworld, hell.’
They understand: ‘It’s impossible that someone who has engaged in good conduct of body, speech, and mind could, for that reason alone, when their body breaks up, after death, be reborn in a place of loss, the underworld, a lower realm, hell. But it is possible that someone who has engaged in good conduct of body, speech, and mind could, for that reason alone, when their body breaks up, after death, be reborn in a good place, a heavenly realm.’ That’s how a mendicant is qualified to be called ‘skilled in the possible and impossible’.”
Do good to others and keep your happiness.
That would be win-win for both sides.
What you mention sounds like sacrifice:
it’s when one sacrifices time,
wealth, or another thing for others.
Hard it is to provide a more specific reply,
unless you elaborate and provide example.