Reddit reviews Stealing Fire: How Silicon Valley, the Navy SEALs, and Maverick Scientists Are Revolutionizing the Way We Live and Work

You've got what I call the 30s depression...Office Space perfectly illustrates how many men feel in their 30s...

Fight Club gets it...

If you aren't in the gym lifting weights, I'd highly recommend it.
>I see them move from their offices to their cars and on to their suburban homes. They stress out constantly, they lose sleep, they eat badly. And they behave badly. Their egos run wild; they become motivated by that which will eventually give them a massive stroke. They need the Iron Mind. Through the years, I have combined meditation, action, and the Iron into a single strength. I believe that when the body is strong, the mind thinks strong thoughts. Time spent away from the Iron makes my mind degenerate. I wallow in a thick depression. My body shuts down my mind. ~ Henry Rollins, The Iron and The Soul

I know how you feel, we all do...a month off is a long time, especially for those who never get that amount of time off. If you can travel somewhere for a week or two - do it (go overseas, Thailand, Japan, Brazil, etc).

I've always believed everyone needs three things to be happy:

1. Someone to love - that's why we are here, being over 30 makes this even more difficult I know, just keep your mind open and don't waste any opportunities. We are social animals, spend time with friends and family if that's possible.
   
   
2. Something to do - this can be anything, upping your skills for a job (programming, math, reviewing old college text books, studying up on ASME, ASTM standards, etc), exercise (weights, yoga, running), learning a new language (Duolingo can be fun), anything you can think of! Having something with measurable goals can help because achieving something, anything will improve your mood and well being. Just remember - idle hands are the devil's workshop.
   
   
3. Something to look forward to - this can be a vacation (always planning that next vacation gives me a boost), a birthday, an event coming up...anything that you are truly looking forward to! I also link this to hope a little, we all look to the future so it may as well be a bright future. Like I said before, travelling solo is great, you're always on the go, you've got lots to see and do and you can meet a lot of people if you plan it right (check out r/solotravel) and stay and mingle in areas with other traveler's, especially solo travelers (like hostels).
   
   I'd like to recommend two books to help you out, Atomic Habits and Stealing Fire if you're interested in self improvement.