I had many attempts at writing my language from the age of 14 to the age 17 with no success: the problem I did not any thing about theory (grammars, parsers, ...)!
The beauty of Forth is that parsing is trivial, just read a space-delimited word from the input buffer and do a simple string lookup through a linked list. The syntax is whatever you want it to be. For me, I modeled my interpreter/compiler heavily off of the jonesforth implementation in x86 assembly.