I have a devotional by Watchman Nee called The Lord Is My Portion. In the reading for January 22nd, Nee meditates on Matt 14:30, which reads: 

But when he saw that the wind was boisterous, he was afraid; and beginning to sink he cried out, saying, “Lord, save me!” 

Nee makes this comment: 

In walking upon the water Peter should not have looked at the strong wind. He has the word of the Lord; he therefore ought not look at the wind and the waves. In looking at these things he easily forgets the Lord’s word. Without the word, one should never walk on water in the first place, even if everything is calm. Since walking upon the water does not depend on the wind and the wave, one should never look at these matters. One should look only at the Lord. 

Isn’t that true of assurance, too? 

Basing your assurance of salvation on your works and behavior is like Peter looking at the wind and waves—it can only produce fear, not assurance. Your life is too tumultuous, rocky, and unpredictable to be the basis of assurance. 

However, you do have Jesus’ word: 

“He who believes in the Son has everlasting life” (John 3:36). 

If you believe, everlasting life is your present possession. 

The winds and waves of your life might send a different message, but as Nee says, “one should never look at these matters. One should look only at the Lord.”