Bad karma refers to a series of negative events and consequences that occur from bad choices and poor decisions that an individual makes. If you spend your life being selfish and self centered then you should not be surprised when you are unlucky. Reaping what you sow is a spiritual concept that means if you do good then good will happen to you, but if you do bad things that harm others you will end up having negative events and unfavorable consequences in your future as well.
Don't blame God for what you brought on yourself! Take ownership and move on.
No matter how bad people treat you, never be a bad person to take revenge.
If you get that gut feeling that something isn't right about a person or situation, trust it.