As I pondered this question this morning, my first response was nothing. God has not given me a spirit of fear (2 Tim 1:7). Then, as I meditated more and more on the question, I realized that I fear not remaining faithful. In the last days, even the elect will be deceived and fall away (Mathew 24:24). If Lucifer, a covering angel, could walk away, what makes us strong enough not to walk away? Only the Lord can give us the faith and resolve needed to remain faithful to Him. We can not do this of our own accord. If you think you can, then you are already deceived.  

“Now the Spirit expressly says that in latter times some will depart from the faith, giving heed to deceiving spirits and doctrines of demons, ” 1 Tim 4:1

The only fear we should have is the fear of the Lord.   

“In the fear of the Lord there is strong confidence, And His children will have a place of refuge. The fear of the Lord is a fountain of life, To turn one away from the snares of death.” Proverbs 14:26-27