In regard to books I would recommend Sun Tzu's The Art of War and Machiavelli’s The Prince, which if nothing else should provide some useful tools for chugging through daily life. These two works will often come with each other for a fairly good price and as both of them are within the public domain, they can also generally be acquired for free. While you're at it I'd also recommend that you acquire the book How to Win Friends and Influence People by Dale Carnegie. Number 5 on the list below more or less explains why. The later book is not within the public domain but you should be able to find it for a few cents at any used book store. Now for the non-literary mentions:
1. Cheesy 80's Music: Believe it or not, investing in an IPod collection of cheesy motivational music from the 80's is a great way to build up energy. I not only recommend Eye of the Tiger, I Ran by Flock of Seagulls, and Push It to the Limit of Scarface fame but also the oft-overlooked Hearts On Fire of Rocky IV. Any sort of fast paced music will generally work for this.
2. Aerobic Exercise: Aerobic exercise is great for warding off physical fatigue and increasing the level of aggression-causing testosterone, which will often lead to a more competitive mindset. Anaerobic exercise is also beneficial for similar reasons in the longer term.
3. View Life as A Game: There is an oft-quoted theory that it takes 10,000 hours of work in order to master a particular discipline. You mentioned seeing life as an RPG. In that regard I recommend that you view even the most menial task as "Level Grinding" and the more complex one's as a game to be mastered. Anything becomes epic when you give it a cool name such as "Luck" or "Agility". Measure each of the skills required for the task at hand and give each of them an estimated experience points required for mastery or a required practice quota to meet the next level.
4. Set Daily Goals And Meet Them: Set particular timeframes until which you must accomplish a particular task. For example, if you have fifty items to place onto your online storefront, attempt to finish the task by 2 P.M.
5. Read About Required Skills: Reading a manual or guide on how to apply a set of skills may very well motivate you to test them out. This can be true for engineering projects, books on computer programming, pamphlets on the basics of musical production, notes on foreign languages, guides to starting a business, or anything else for that manner.
6. Read About Skilled Individuals In Your Field: Whether the person that you are reading of is a historical figure or contemporary master, reading about successful individuals can be inspiring. For instance, an unusually large amount of inventors have been inspired by reading of Thomas Edison in their youth, even down to the famed Nikola Tesla.
7. Create A Vision For Success: Whenever the current situation gets you bogged down attempt to the visualize the particular endpoint for which you are striving for. The Beatles, for instance, played for 178 nights within one year while they were first starting out, but at a large portion of each of these nights, they would allegedly play as if that night would be the event at which they would finally break out.
8. Self Hypnosis: The effectiveness of this technique will depend on your suggestibility. When you must finally sleep, plan what you will do as soon as you awake and repeat it to yourself. This has never failed in causing me to get to work at the beginning of the day.
The majority of these methods seem to appeal to Te, Se, and Ni.