Biblical Absolutes to be sure of

Have you no wish for others to be saved?  Then you are not saved yourself, be sure of that. - Charles Spurgeon

The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. 2 Peter 3:9

Look not every man on his own things, but every man also on the things of others. [5] Let this mind be in you, which was also in Christ Jesus Philippians 2:4-5

If you are living a life of unrepented and continuous (habitual) sin then you are not saved be sure of that.

Except ye repent, ye shall all likewise perish. - Jesus.  Luke 13:3 and 5

If you have not forgiven others then you are not forgiven yourself and thus are not saved be sure of that.

For if ye forgive men their trespasses, your heavenly Father will also forgive you: [15] But if ye forgive not men their trespasses, neither will your Father forgive your trespasses. Matthew 6:14-15

If you are doing things that are not approved of God then you are denying Jesus before men by your actions and are thus not saved, be sure of that.

 But whosoever shall deny me before men, him will I also deny before my Father which is in heaven. Matthew 10:33

If you serve two masters then you are  not saved be sure of that.

No man can serve two masters...- Jesus. Matthew 6:24

There is absolutely no room for compromise in a Christian's life, be sure of that.

I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. [2] And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God. Romans 12:1-2

Prove all things; hold fast that which is good. [22] Abstain from all appearance of evil. 1 Thessalonians 5:21-22