Revelation 14 says that whoever takes the mark of the beast on their right hand or their forehead will drink the wrath of God.
This isn’t like sinning, praying to God, and then He forgives you. This is unforgivable. When you take the mark of the beast, that means you are beyond repentance. But how will people be able to buy food or sell? How can they get medical attention? How will they be able to feed their babies?
This is why Jesus said you better hope you’re not pregnant and living in the tribulation. You will not receive any help from God when you take the mark of the beast.