Eternal salvation is simple, and mankind dose not have to do anything to get it. God, by his sovereign grace choose an elect people before the foundation of the world, (Eph 1:4) and predetermined them to be adopted as his children (Eph 1:4) by giving them to his Son to be a sacrifice for the redemption of their sin on the cross. (John 6:39). Jesus said that he would not lose any of them, but will raise them up at the last day.
After thinking through this very controversial topic especially between Calvinist and Armenians for quite a long time, I have concluded that most people will be lost because of this simplistic view of Christianity.
God chose us through predestination, yes, but in his foreknowledge he chose us.
We also have to choose him.
We serve God with our minds and we cannot serve him mindlessly.
Paul says - Be ye transformed by the renewing of your mind (Romans 12:2)
Also Paul says that we serve the law of God with our minds. (Romans 8)
Rom 7:25 I thank God through Jesus Christ our Lord.
So then with the mind I myself serve the law of God; but with the flesh the law of sin.
Peter gives us a clear picture of the process of salvation.
1Pe 1:2
Elect according to the foreknowledge of God the Father, through
sanctification of the Spirit, unto
obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
God's grace is sufficient but we should not take it in vain. (i.e. ignore it).
Also sanctification is a process by the Holy Spirit and Paul warns us not to grieve or quench the Holy Spirit. Yes we can quench the Holy Spirit by not living circumspectly.
The most important ingredient of salvation for today is knowledge (faith is foundational) as it was in the days of the Old Testament. (It probably is much more important to day as we have to get that knowledge through the holy Spirit and the word of God.)
In the bible the people got their knowledge through God's emissaries, e.g. Moses, Jesus, Paul, Peter etc and still they messed up.
Hos 4:6 My people
are destroyed for lack of knowledge: because
thou hast rejected knowledge, I will also reject thee, that thou shalt be no priest to me: seeing thou hast forgotten the law of thy God, I will also forget thy children.
Hos 6:6 For I desired mercy, and not sacrifice;
and the knowledge of God more than burnt offerings.
2Pe 1:5 And beside this, giving all diligence, add to your faith virtue; and to virtue
knowledge;
2Pe 1:9 But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins
Paul uses the word wisdom which is synonymous to knowledge.
1Co 1:30 But of him are ye in Christ Jesus, who of God is
made unto us wisdom, and righteousness, and sanctification, and redemption:
Even Daniel brought out the importance of knowledge.
Dan 12:10 Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and
none of the wicked shall understand; but
the wise shall understand.