If Tribulation believers are responsible for their own salvation, what is it that they must do (or not do) in order to maintain their salvation? What will their “falling away” consist of? How can they “maintain their salvation” with no help from God; without the Holy Spirit within them, when they are assaulted by supernatural forces — compulsions beyond mere human endurance? Are they abandoned by God? — “You’re on your own, buddy.” Are they beyond God’s grace and mercy? Exactly what will they have to contend with? If the Temple has been desecrated, how can they participate in the mandatory sacrifices and Holy Days?
Speaking of the time when the anti-Christ will require that everyone take the mark Rev. 14:9 says that anyone who does so will suffer the full strength of God’s wrath, including eternal torment. Then Rev. 14:12 says “This calls for patient endurance on the part of the saints who obey God’s commandments and remain faithful to Jesus.” Rev. 16:15 says Tribulation believers have to keep their clothes with them, a euphemism for keeping themselves righteous to the best of their ability.
From this we see that they can not take the mark, and must keep the commandments as well as maintain their belief that Jesus has paid the price for their sins. This is similar to Old Testament requirements. The difference is that Tribulation saints will know the name of their redeemer, whereas Old Testament saints did not.
Obviously most believers around the world will not be able to attend the Temple sacrifices even when they’re offered. After the Abomination, no one will. This was also the case in Old Testament times, for Jewish people who didn’t live in Israel, or during the Babylonian captivity for example. Life in those times consisted of keeping the Law, daily confession for sins, observing the Holy Days without the sacrifices, and believing in the coming redeemer. The absence of the Holy Spirit’s conviction made it necessary for people to be much more aware of their behavior, as it will after the Church is gone.