There are a ton of variables related your site's traffic and we can't really tell you why you have had a sudden decrease in traffic. Here are a few things you can check though:

1) Did your domain name change, or maybe the referrer-policy header?

2) Ask the entire team responsible for your website if literally anything has changed in the last X days since your traffic has dropped. Look at the commit logs, but also check server configurations.

3) Do you use any other trackers? Does the same drop in traffic display there? If so, then likely your traffic actually dropped. If not, then maybe Clicky is not installed on all of your pages.

4) One thing that might point you in the right direction is to go to the Visitors -> Traffic sources report, and graph each of the items in that report. Do they all show a similar drop off or does one in particular drop off a lot more than the others? For example if the one drop of is "Searches", then a search engine change definitely affected you. Or if it's "Social Media" then maybe Ashton Kutcher unfollowed you and your popularity started a downward spiral. Anything's possible.