What does YMMV mean? Maybe I'm stupid.

In other words, my success may not guarantee yours

In other words, you may not experience the same service you read in somebody else's review.
Read the self help center (which you can find at thr top of the page by the red and white life preserver.) among all the other useful information about the hobby and TER, you will find a list of definitions and commonly used acronyms.
You can also find many of these acronyms on urbandictionary.  

Thanks for the help! I would never have gotten that one alone.

Or even a google search may work.

Just in case he missed it in my post.