I usually watch an anime when I'm in a slump. I find they tend to spark ideas and inspire me with character designs. Also, make a little bit of a plan for yourself. Think about the character you want to design, the triumphs they can experience, and the down falls they will have to endure. Characters that struggle are a lot more interesting than more powerful ones. Music is also a good choice. It can get those creative ideas flowing and start to help you out of the slump.

Pretty much, put yourself out of your comfort zone and see how that goes. RPing should never become a chore but if you're enjoying it, then keep it up. 

As for people. Pfth... you can't expect that comfort bubble to stick around your whole life. If people leave then look at others and try to get to know them. I've been on so many forums before, met people I like, and people I hate, but after being here for a few months I can say that I have a group of friends that I can really appreciate. That's the whole reason why people join a forum, to meet others. The role playing is just a common interest that connects us. Once you forget that you've essentially forgotten the key reason why people role play.