To get to understand whether or not you would lose your salvation if you stop believing, you need to know this. Many years ago, God promised humanity the coming of the Messiah through His holy prophets such as Moses De 18:15, Isaiah Isa 7:14, Jeremiah Jer 23:5, Ezekiel Eze 17:22, Daniel Da 7:13, etc. The purpose of the Messiah’s coming was to bring salvation to mankind, both Jews and Gentiles, for it is written:
And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the end of the earth. Isaiah 49:6
In due time, God fulfilled His promise by sending the Messiah who was born into the world and named Jesus – born in Bethlehem but raised in Nazareth. The Messiah Jesus, for the course of bringing salvation to mankind, died on the cross of Calvary and was buried. But on the third day of His death, He resurrected from the dead, and forty days after His resurrection ascended to heaven to sit on the right-hand side of the Father.
God has promised mankind that whosoever believes in Jesus that He is the Son of God, that He is the Messiah, that He died, and that He resurrected from the dead, such a person shall be saved. Any good thing that Jesus has to offer can be accessed through faith. Without faith, it is utterly impossible to receive anything that comes from Jesus such as salvation.
None of us people of this generation ever physically encounter Jesus; we never met Him, touched Him, saw Him, heard Him, walked with Him, etc. In fact, whatever happened to Jesus took place almost 2000 years ago before us. Yet God has promised salvation to anyone who, though never encountered Jesus physically, believes in Him as His Lord and Savior. And he receives this salvation as a package of blessings comprising of Justification, Ga 2:16; Regeneration, 1Pe 1:3, 2Co 5:17, Sanctification, 1Co 6:11; Forgiveness, 1Jo 1:7; Eternal life, John 3:16; etc.
The big question is can you lose your salvation if you stop believing in Jesus? Yes. From the build-up above, it is too obvious that since faith in Jesus leads to the receipt of salvation, if you cease to believe in Jesus you are automatically cut off from salvation. Bear in mind that salvation and any benefit, help, or profit that comes from Jesus, at any given time, is exclusively for those who believe in Him. It is written:
He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. (Joh 3:36 KJV)