It is written God knows those who are His and everyone who names the name of Christ should depart from iniquity, and by doing so we are claimed as His own and promised eternal life through faith in Christ. (Titus 1:1-2).
Through Christ we are redeemed by His shed blood, and by being the perfect sacrifice, He has made it possible for us to have a reservation in heaven the promise of an eternal inheritance. (Hebrews 9:12-15). Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us. For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God? And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
Just like any reservation we may make here on earth to stay at a place we also may break our reservation made for heaven if we were to return to a sinful life and forget what Christ did for us at the cross. (1 Peter 1:3-9). Blessed be the God and Father of our Lord Jesus Christ, which according to his abundant mercy hath begotten us again unto a lively hope by the resurrection of Jesus Christ from the dead, To an inheritance incorruptible, and undefiled, and that fadeth not away, reserved in heaven for you, Who are kept by the power of God through faith unto salvation ready to be revealed in the last time. Wherein ye greatly rejoice, though now for a season, if need be, ye are in heaviness through manifold temptations: That the trial of your faith, being much more precious than of gold that perisheth, though it be tried with fire, might be found unto praise and honour and glory at the appearing of Jesus Christ: Whom having not seen, ye love; in whom, though now ye see him not, yet believing, ye rejoice with joy unspeakable and full of glory: Receiving the end of your faith, even the salvation of your souls.
We are to have a healthy fear of God who knows how to deliver the godly out of temptations, but there is also another reservation that is not heaven bound where the unjust have a reservation to be punished. (2 Peter 2:9).