1) Click the icon pictured below in your dock.

2) At the top of the screen, select Go and Go to Folder.

3) In the prompt pictured below, type ~/Library/Keychains and click Go.

4) In the folder that appears, select all the items by pressing Command + A then press Command + Delete to delete them.

5) Once they are deleted, restart your Mac.

Note: After restarting you may be presented with an option to Create New Keychain or Use Existing Keychain. Always choose Create New.