Jesus says that he who believes in Him, he who trusts in His work and not their own, has eternal life. Please notice the verb. Not "will have", or "might have", or "one day you will"... Jesus says he who believes has eternal life!
Now, some people teach that it is possible to lose your salvation, or to lose eternal life. But if this is true, was it really eternal? If it lasted a few months, a year, or twenty years, was it eternal? No! It was anything but that. In contrast, look at what Jesus says:
He who believes in the Son has eternal life... John 3:36
..he who hears My word and believes in Him who sent Me has everlasting life and shall not come into judgment..."John 5:24
Look up these verses about how seriously God takes our eternal life and how far He is willing to go to make sure we don't ever lose it.
John 6:39 John 10:28-29 Ephesians 1:13-14 1 Peter 1:4-5
YOUR SALVATION IS BASED UPON ON JESUS' DEATH, NOT YOUR BEHAVIOR OR ACTIONS. IN THE SAME WAY, YOUR ETERNAL LIFE IS NOT BASED UPON WHAT YOU FEEL OR DO ONCE YOU ARE SAVED, BUT UPON WHAT GOD HAS PROMISED THROUGH CHRIST.