Documenting programming

Now that is another story, I already know that Programming is the easy part, documenting what the programmer does is completely another tough part.
It is again happened, I have to do the documenting for the ACuSys system, it is taking me a lot of time, and need to remember a lot of old stuff I did and why I did that.
However, the client is happy with it and might have some new chances in the future to do more like these.