Former congressman Aaron Schock (R-Ill.) gave his farewell speech to the House of Representatives on March 26, saying that as he goes through this "valley in life" he looks to former president Abraham Lincoln for inspiration. (AP)

Days ahead of his planned resignation from Congress, embattled Rep. Aaron Schock (R-Ill.) delivered a farewell address on the House floor Thursday afternoon in which he said he was departing with "sadness and humility" and he vowed to "work tirelessly" to make it up to those who he has let down.

In his speech, Schock thanked his constituents and staff. He said he was proud of legislation he helped pass to create jobs and improve veterans' benefits. He said it was regrettable that he would not be around when Congress passes tax reform.

"There was, is and will be so much to do. And I'm honored to have played a small part in making a real difference," said Schock.

Schock, who announced his resignation from Congress last week amid swirling questions about his spending and documentation which drew scrutiny from ethics officials, looked to Abraham Lincoln — who once held his seat — as a source of inspiration in his difficult situation.

"I also know that every person faces adversity in life. Abraham Lincoln held this seat in Congress in one term. But few faced as many defeats in his personal, business and public life as he did," Schock said. "His continual perseverance in the face of these trials — never giving up — is something all of us Americans should be inspired by, especially when going through a valley in life."

Schock will step down March 31. The Justice Department is investigating whether he broke any laws.

"I know that this is not the end of a story but rather the beginning of a new chapter," Schock said.