Malicious external magical influence (magical hex or attack) can be "initiated" by people or «higher forces».
People can affect you «accidentally» without a proper understanding of their actions. For example: during a quarrel, a man on strong emotions wishes his opponent different «bad» things and something happens. The evil eye he has, someone will say.
The other example is passive jealousy, where a person doesn’t seem to do anything, but just hates you so much and hurts you by jinx and yourself with it, or a person is just an energy vampire, constantly sucking energy from you. Also, a person may have a different energy type than you can receive or give, so one of you or both will feel bad with each other.
Why stand we here trembling around, calling on God for help, and not ourselves, in whom God dwells?
Another thing, when someone enchants you with intent.
The main point is that human beings, because of their imperfect nature, cannot by themselves cause or remove a real serious curse or damnation. Serious magical influences are produced and/or initiated by a higher power only, but a man can participate as a tool or voice of the higher will.
There are common laws of the universe that if you break, you will have to answer. People cursed by reasons only, one of which can be your weakness.