Spend less time watching tv, movies and playing video games and browsing the internet.
go to the gym 4-5 days a week.
Sleep more.
Eat better. Cut down on sugar, pasta and rice; load up on meat, eggs vegetables and eat fruit when you want something sweet.
Try intermittent fasting. Try going until midday before eating anything except water/sugarless black tea or coffee. Once you get used to this, try going one day a week where you don't eat until the evening.
Read at least one book a fortnight, check out book mentioned
here (click on the headings 'More Book reviews X' to see the actual posts) for some interesting stuff. Non-fiction>>>>>fiction
Take up a martial art and take it seriously; I recommend muay thai, or Brazilian Jiu Jitsu if you're not into hitting/being hit.
Cut down on the
caffeine
Learn to meditate, it has enormous benefits for your brain and state of mind
Masturbate no more than twice a week. Sounds dumb or even counter-intuitive in terms of 'fun' but if you do it to often the hormonal effect is such that you get less enjoyment from other things. Its sort of like being hungover all the time without realising it (if you're the sort of person who does it daily).
Basically,
entertainment is not the cure for chronic boredom, and indeed our constant exposure to it actually helps fuel boredom. You'll notice that most of these things don't sound super "fun" in the boredom-curing sense, but the key is to improve your physical and mental health and stop experiencing 'high reward' activities (i.e. instant gratification) and move to more 'low reward' activities. This stops your brain from expecting constant stimulation and so it can get more enjoyment out of simple non-highly stimulating things. Going to the gym for instance is not most people's idea of fun, but putting in hard work day in day out and gradually seeing results (getting bigger and stronger) is a much healthier and long-term way of being happy and contented. You certainly don't have to do all of those things (not masturbating as much, sleeping more and spending less time on on computer/tv are vital though), but give them a try.