Sorry to hear that you're going through this. Sorry to see that your long time cat passed away. A few months after my 18 year old cat passed away I started volunteering at a local cat shelter. It helped me feel better - getting out of my normal routine to do something for others felt good. Plus playing with the cats is a lot of fun.
Maybe that's something you could look into to help you get through this tough time.
I ended up adopting one of the cats after about 1 month of volunteering.