When you decide to re-blog your own stuff or take an old post and freshen it up a bit that can be a good thing. An old post can be seen in a new light by new eyes who are just now discovering your blog.
When your creative juices are running low, you can find inspiration from things you have done before. Be careful not to get too repetitive but enjoy the process of introducing your followers to your blogging journey. I would advise doing a short introduction to the post you are re-blogging to set up context and to let folks know this is a golden oldie.
It can be fun to take a look back until new ideas for new posts come along.