After wasting a lot of time until finally finding a solution, I decided to share this with the community.

The problem:

convert
dyld: Library not loaded: /usr/local/opt/little-cms2/lib/liblcms2.2.dylib
  Referenced from: /usr/local/bin/convert
  Reason: image not found
Abort trap: 6

This kept happening even after updating ImageMagick:

brew upgrade imagemagick

so what's the solution?