Some say that Avraham Avinu was afraid because he killed so many people, or because he had to do with Melech Sedom, etc. Just as Hashem had to reassure Avraham Avinu not to worry since his Schar is very great, so many of us need to be M'chazek ourselves, and say: אל תירא ינקלע, שכרך הרבה מאד Don’t worry “Yankel”, your Schar is very great! One of the main Yetzer Hara’s of our generation is Atzvus (sadness) about our spiritual status.
We all have tons and tons of Mitzvos and Zechusim, but the Yetzer Hara makes us worry all day about our Aveiros. And sometimes this is actually a Ma'ala, since we want to improve. We can suggest that: אל תירא אברם שכרך הרבה מאד means that since you have so much pain and worry about your sins, this in itself will give you much Schar, since you are a big Baal Yissurim with all this worry.
