Many people like to talk about the curses in the old testament as if they apply to people who have been saved or call Jesus their Savior. They don't. It is a lack of knowledge that destroys you.
But you will ask, "What about when it says that God will visit the sins of the father to the third and fourth generation?"
To clear that up, look at the context -
‘The Lord is slow to anger and filled with unfailing love, forgiving every kind of sin and rebellion. But he does not excuse the guilty. He lays the sins of the parents upon their children; the entire family is affected—even children in the third and fourth generations.’ Numbers 14:18
Notice that God is in the business of loving people and forgiving every kind of sin and rebellion. But He does not excuse the guilty. Who are the guilty? In this context the would be the people who didn't make atonement for their sins through the sacrifice system that God created for them. If you made sacrifices, your sins would be forgiven. But for the rebellious who wouldn't listen to God, they would be punished. The curse is death. That is THE curse. It was put into effect by the Law.
But I said earlier "You are either cursed or you are in Christ."
Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: "Cursed is everyone who is hung on a tree." Galatians 3:13
This is an interesting concept. If Christ redeemed you (made you right with God) then can you be cursed by God? No.
"Yet you ask, 'Why does the son not share the guilt of his father?' Since the son has done what is just and right and has been careful to keep all my decrees, he will surely live. The soul who sins is the one who will die. The son will not share the guilt of the father, nor will the father share the guilt of the son. The righteousness of the righteous man will be credited to him, and the wickedness of the wicked will be charged against him. Ezekiel 18:19-20
This passage in context of the Law but the principle still applies to us under Grace. When we turn to Jesus and accept his free gift of salvation which brings righteousness, God doesn't remember our sins and we are not cursed. We cannot be! Can Christ curse himself? Aren't we the body of Christ?
When you are saved, you are saved.