protecting the creditor as well as the debtor

Even though the superficial reading of the parsha of shemitas kesafim sounds like a windfall for borrowers who have overextended themselves and need debt relief, in fact, the Torah is equally concerned with protecting the creditor from financial loss.

Rashi writes that there seems to be a contradiction between the statement (15:4):

 אֶ֕פֶס כִּ֛י לֹ֥א יִֽהְיֶה־בְּךָ֖ אֶבְי֑וֹן כִּֽי־בָרֵ֤ךְ יְבָֽרֶכְךָ֙ יְהֹוָ֔ה בָּאָ֕רֶץ אֲשֶׁר֙ הֹ׳ אֱלֹקיךָ נֹֽתֵן־לְךָ֥ נַחֲלָ֖ה לְרִשְׁתָּֽהּ׃

 and the statement a little later in the parsha (15:11):

כִּ֛י לֹא־יֶחְדַּ֥ל אֶבְי֖וֹן מִקֶּ֣רֶב הָאָ֑רֶץ

It's clear from the question that Rashi read the pasuk אֶ֕פֶס כִּ֛י לֹ֥א יִֽהְיֶה־בְּךָ֖ אֶבְי֑וֹן as referring to those in need.  Ibn Ezra explains (see Seforno, Malbi"M, Abarnanel) understood the pasuk that way as well, and writes that even though the Torah commands that all loans be forgiven during shemitah, potentially wiping out lenders, the Torah wants to reassure:

דע כי זה שצויתיך: שלא תגש לאחיך (דברים ט״ו:ב׳), אין צורך אם היו כל ישראל או רובם שומעין לקול השם, אז לא יהיה בך אביון שהוא צריך אליך להיותך מלוה אותו.

So long as most people are doing mitzvos, there will not be that many people in debt or in need with outstanding loans, and so lenders won't suffer extraordinary losses.  

Netziv, however, read the pasuk as referring to the lender:

שלא תגרום השמטת כספים שתהיה (אתה) אביון,

He does not mean there is some supernatural protection against falling into poverty as a result of forgiving debt, but rather he sees this as an encouragement to Beis Din to institute takanot like pruzbul that protect creditors.  כי ברך יברכך ה׳, G-d wants to bring them blessing as well, not destroy the economy or their livelihood.