I have decided I'm not going to repay back gifted money when I said once that I would
How could you? Why won't you pay them back?
I don't want to. I don't owe them anything.
I understand where you're coming from, but you did say you would pay it back.
But it was a gift and I no longer think I need to pay it back.
No problem, just be careful next time of what you say. Even though there is no obligation to pay back gifts, you still had your word that you did which you went back on. Both ways are a little rude, so how about a compromise and just gift them something for now instead?