An atheist said:
I am better than Christians. Christians are good because they fear the pains of hell. I am good because I believe it is the right thing to do.
Good luck doing that without God.
The reason for our existence is that we should love God in this life in order that we should be with Him in the next. Did you notice the continuity? There is no real separation between this life and the next. If you love God in this life, that entails obeying Him and keeping all the Commandments. By definition, that means being righteous. Then:
Hebrews 12:22 But ye are come unto mount Sion, and unto the city of the living God, the heavenly Jerusalem, and to an innumerable company of angels, 23 To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect, 24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.
Even though you are still alive, you are already walking with the Saints. When you die, you will continue walking with the Saints in the presence of God.
However, if you deny the existence of God in this life, it then becomes very difficult to sustain an attempt at righteousness. In addition, those who deny God's existence will not ask for His grace which He grants to all who pray.
The main thing though, is that you have denied Him in this life and therefore He will deny you in the next.
Matthew 10:32 Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven. 33 But whosoever shall deny me before men, him will I also deny before my Father which is in heaven.
Unless you change your mind between now and the end of your life, you have made your destiny.
Deuteronomy 30:19 I call heaven and earth to record this day against you, that I have set before you life and death, blessing and cursing: therefore choose life, that both thou and thy seed may live:
Romans 6:15 What then? shall we sin, because we are not under the law, but under grace? God forbid. 16 Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness? 17 But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you.