Can you lose your eternal rewards?
The Bible doesn't really mention if eternal rewards can be earned and then later lost. However, it does plainly say that many people will not receive a large portion of the rewards they thought that they had coming to them.
Paul, in Corinthians, says that all of our works will be tested by fire, and we will only get to keep the valuables that the flames do not destroy. Nearly all Christians have a good idea of what they've accomplished in life. Many of the folks who think they are due a sizable reward will be shocked when the fire of judgment reveals that most of their deeds were based on vain self-glory.
"For no other foundation can anyone lay than that which is laid, which is Jesus Christ. Now if anyone builds on this foundation with gold, silver, precious stones, wood, hay, straw, each one's work will become clear; for the Day will declare it, because it will be revealed by fire; and the fire will test each one's work, of what sort it is. If anyone's work which he has built on it endures, he will receive a reward. If anyone's work is burned, he will suffer loss; but he himself will be saved, yet so as through fire" (1 Cor. 3:11-15).