I’m not sure I have found anything as fun as the “good ol days” but I have found a ton of stuff to fill the void, lots of volunteer work, crafting, small do it yourself remodeling projects, taking classes on upholstery, and school part time all keep me busy. I know how hard it is when 99% of the people you hung out with are the people you drank/ used with; your party buddies, but I found the real friends from that group are willing to respect your desire not to use and will not drink around you. I also found the extra cash you save comes in handy to have pamper you days, a spa day is a million times more relaxing than a night of drinking and waking up feeling like crap.
It takes time to find things to fill the void, I have been drug free 17 months and I will not lie, I still miss certain parts of my old party life, but I know this new me is a million times more happy. Just keep trying new things or old things you used to love doing and I am sure you will find something therapeutic to help with the initial boredom.
Hope it helps to know most of us went through the phase of what to do now that we're sober.