look to one's laurels - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Protect one's preeminent reputation or position, especially against a threat of being surpassed. For example, Your opponent's done very well in the practice, so you'd better look to your laurels in the actual game. This idiom alludes to laurels as the traditional material for making a victor's crown. [Late 1800s]