On one hand there is the drive to improve, to excel at what you do. On the other often disproportionate effort and time expended.
Lots of people mention the 10,000 hours to become an expert posited in Malcolm Gladwell's The Tipping Point. Let's face it, 2 and 1/2 hours per week for eighty-three years and 4 months (assuming you spend 4 weeks a years not gaming) may be a bit too long for some of us to get it right.
There are those who game more or longer. The figures scale though quantity is not always synonymous with quality.
Accept and embrace imperfection. The refinement process may be laden with mistakes (a proven way to learn) and missed opportunities. Plan instead on success and leave passive-aggressive critiques to those who never get game invites but whose war stories rattle on how poor a game was ten years ago. A word to those types: learn from the mistakes and move on - everyone else has. Things may also have changed a bit since your last experience.
There are strategies to help minimise the impact. They've been mentioned before elsewhere in various places but the core ideas are essentially sound and have been proven to work.
- Know what success is. Running a game can be like planning a party or as simple as getting a few friends round for beer, pretzels and a laugh. Different games have different requirements, it is worth thinking of what you're out to achieve. High Art may be unmanageable on your budget and environment. Work with what you have and use tools to get where the good stuff is.
- Use the 80/20 rule. Pareto's principle of 20% effort yielding 80% results can be used to great effect. Remember no plan survives contact with the players so 100% preparation is counter-productive, particularly as there are variables you won't know until they happen. Accept it, re-route or smooth over speed bumps and focus on the 80% at each pass. According to Zeno, two passes means you've done 96% of the work needed.
- Get things lined up. Your players need a reason for their characters to be there, a challenge to beat and some perceived or actual recognition or reward for their efforts. It is worth thinking of how to provide those things and how to bolster obvious weak points say an army of minions for your evil wizard for example. Your players will make it clear if there is a shortfall in one of those things - accept the feedback with good humour.
- Compartmentalise. A house without walls is a gazebo (see rule 1), a wall without bricks is a windbreak. Cut up the preparation into discrete tasks. Once you have done something, stop otherwise you fall prey to Parkinson's law. Look at how it fits together and if it works, keep unless you have better to hand. If you have the luxury of time think about how to improve those compartments. They're called modules for a reason.
- Stand on the shoulders of giants. Creativity is hiding your sources; while sites like TV Tropes and Arcana Wiki can show the strings holding your dragon up, there are plenty of sources and places to inspire you - from the One Page Dungeon Codex to resources in recession-proof gaming posts. And this is before opening a magazine or sourcebook.
- Only create what you need. This may vary by approach, the backstory may feed other elements. Put yourself in a player's chair and ask "What do I need to know to engage with this?" Then provide it - if pressed for time, free writing may be a poor choice. Listening to your players is the smart way to discover what you need to focus on and plays to the awful realisation that your players may want different things than you do.
- Re-cycle your mistakes. That lame villain you canned for your fantasy game may make a great supervillain with tweaking. Slush files are good to keep for future reference. Most people can use automated search to find something appropriate. Combined with point 4, you can create a ready-made game in less time than you think - maybe even 60 minutes.