Hash-m goes "out of His way" to save a Tzadik more than He does to save a wicked person. This sometimes involves minor miracles that are done for the benefit of the Tzadik (such as having the right person appear at the right time to help him). Because of this, the Tzadik is constantly worried that he might have "eaten" his share of the World to Come through the Divine Help he received in this world. It was for this reason that Yakov Avinu said "Katonti...", see Rashi to Bereishis 32:11. Hash-m reassures that Tzadik that this is not the case.

According to Rashbam's second explanation, the Tzadik is worried about the opposite effect; perhaps Hash-m will save all of the Tzadik's merits to be repaid in the World to Come, and the Tzadik will not receive the "Peros" of his deeds in this world, making it much harder for him to continue doing Mitzvos. Hash-m informs the Tzadik that he will even receive Peros in this world and it will not lessen his share in the World to Come.

M. Kornfeld