It's not selfish at all. You'll be opening up the job to someone else who does need it. It's the opposite of selfish. Good for you, and good for the person who gets your job. Then you get the chance to move on to greener pastures.

I don't understand the guilt, besides you feeling "lucky" to have the job when others don't have one. You're lucky you don't need it right now. You should be proud that you've done well and enjoy the success. It's nothing to feel guilty over.