I find the type of material I use has a major bearing on whether I
enjoy teaching lessons or not. So, when I feel the material is stale, I
look for more, or even better; I write my own. I think of something
that interests me, and then write a lesson on that subject.
News articles can be good material too, but are sometimes too serious
for me. Thankfully, there are many sources of humourous 'news' on the
internet (notably The Weekly World News), which may also provide
inspiration. Dialogues and role plays can also be fun. Write new
material, or modify existing material to tickle you own funny bone.
This can be a LOT of fun, and students are usually delighted when the
material they are using applies directly to their own locale or
situation.
I hope these suggestions are of help to you in your situation.
Regards,
Mike.