With only 128MB RAM, just about [i]any[/b] GUI IDE will be dead slow. I've never found life any fun unless I had at least double that, and these days, I'm running a full 1GB because in addition to the IDE, running
J2EE debug session really eats memory.
If you can stand living your life on the CTRL and ESC keys and working on a character-mode terminal, your best bet is probably to install Emacs and the Emacs JDE package. I've used it in as little as 96MB of RAM on a P-200 (with no windowing system running), though even it can be slow when it comes to auto-completions.
It won't give you everything that Eclipse will, but it can be pretty helpful.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.