Install this extensions
https://chrome.google.com/webstore/detail/bmstats-stats-for-your-bo/ogdcicncikokgpojepfdikmpeghoepig
Watch the numbers
Look at the stats
Clean your bookmarks and watch the stats improve :]
What ’bout Firefox you might ask?! I made a similar extension for Firefox. Check it out here: https://romanluks.eu/blog/how-to-motivate-yourself-to-clean-your-bookmarks/