Never say never is a good piece of advice for us to remember. In many situations it is unwise to say you would never do such and such because, after all, we aren't omniscient - we don't know what the future will throw at us to make us eat our words. Furthermore, we aren't omnipotent - circumstances may arise that will cause us to give in and back track and do what we said we would never do. However, if one were omniscient and omnipotent then that person could afford to say "Never!"
This is something that God in His Word says time and time again. For instance, He says that the Old Testament sacrifices can never take away sins (Hebrews 10 v 11). You may wonder what relevance that has to you today, but the relevance is this, if those divinely instituted, God-ordained sacrifices could not take away sins then our sacrifices can't do it either. So many people are depending on the sacrifices they make to pay for their sins and satisfy God, but our sacrifices aren't sufficient to pay for even one of our sins. The good news of the Gospel is that the sacrifice of Christ is sufficient to pay for every one of our sins. We need to stop depending on the sacrifices we make to pay for our sins and bring us into a right relationship with God (sacrifices of time, effort, energy and finances), and we need to depend on the sacrifice Christ made instead.
The Lord was able to say regarding those who came to Him for salvation, "I give unto them eternal life; and they shall never perish..." (John 10 v 28). This is the assurance that those who trust the Lord for salvation have. Their eternal destiny is fixed, their fortune is made, the Lord says they can never perish.
Those who have this assurance for the future also have a wonderful assurance for the present, the Lord says "I will never leave thee, nor forsake thee" (Hebrews 13 v 5). The Lord not only saves those that turn to Him, but He also enters their lives and walks with them every step of life's pathway.
However, there is something else to keep in mind: the Lord spoke about the awfulness of being lost, and He warned His hearers that in that place the worm does not die and the fire never shall be quenched (Mark 9 v 43). It is tragically the case that for those who die without salvation, their eternal destiny is fixed, their doom is sealed, they are lost and shall never be saved.
When the Lord says never, He means never. This is a thrilling word for the Christian - saved, never to be lost. This is a terrifying word for the non-Christian - soon to be lost, never to be saved. You can be saved now by turning in repentance to Christ, but remember, it may be now or never.