Never thought of having a journal. Do all the notebooks full of ideas count? Seriously, I have notebooks everywhere - big and small. During periods of cleaning, I'll go through them and throw away whats no longer interesting or working.
It's good to look on them, because I've been doing this since 2008 and each year, seems like month, things change. Some techniques are evergreen while some have to be thrown out.
I also have a lot of files on Google Drive. It's not a journal, but all these files do provide me with a history of things I was working on at one time.