I completely understand your thoughts and feelings, coming from the having 'been there and done that' same ol' routine day in and day out and what happened to the fun me????
I want to recommend something a little different than the other posts about making plans and commitments to going out....
Shift your focus to making plans on having another couple with kids over once a month for a simple pot luck, wine and games. Those are some of my happiest memories, sharing easy, favorite recipes, the kids are happy playing, great music is playing....ah, life was simple. And you don't have to be a gourmet chef and you don't really have to clean the house....I read that most people are more comfortable in a home if at least one of the common areas is messy, some people just can't relax in a too clean of an environment. So that was always my excuse for an untidy home - to make others feel comfortable.
And our new favorite family game is "You Don't Say!" - we are all laughing constantly not just during the game, but days later when we think of how someone tried to describe something. It's really fun.
So, I would recommend taking an inventory of what you used to do for fun and do a little brain storming for what you can do NOW that includes your family. There is way more to life than just 'going out' for going out sakes - start planning ahead for visiting museums, national parks, children's theatres, local high school and university performances, local art fairs....
Ask your kids and hubby what evening activities they would enjoy....crafts, sports? Also, don't go overboard. I can only handle about 3 nights out per week, anymore and I'm an absolute grump.
P.S. - I'm 50
Post-ad: I am not kidding, but just after I posted this response, I received an email from an old friend, who found me on facebook because our post graduate daughters still stay in touch there. He was a dear friend formed during those dinner parties at home when our kids were in elementary school. I am back in with elementary school age kids again and he is remarried in Bogota on business.... and I know we'll still talk about cooking, and traveling and kids....and wine.