Sherlock Holmes is the record holder for the most adapted character in fiction. Since his creation by Sir Arthur Conan Doyle, he's been brought into the present, thrown into the distant future, and been the inspiration for everything from a doctor to a teenage girl all the way to crime solving mice and dogs. In recent years, there have been no less than three adaptations going on at the same time. The creators behind the BBC's most recent and wildly-popular outing have stated that, despite the characters and story very much being a product of their time, they decided to do their contemporary update exactly because there's still a lot that pulls people toward these stories. There's something new to be told every time the characters are adapted into a new medium, and the most recent incarnation has its own lessons to teach.
Sherlock did not become the archetype for the insufferable genius by accident. In all his adaptations, he's always shown his incredible brilliance by continually learning new things and conducting various experiments, and even when he isn't, often has a stash of supplies handy (namely a head in his freezer and eyeballs in his microwave.) Even outside of crime-solving, he's shown to play the violin when bored and 221B Baker Street is littered with experiments he's done that didn't relate directly to a case, but that he just did for the hell of it.
Analyzing how bruises form on a body postmortem might not be your idea of a good time, but Sherlock has got the right idea. Constantly learning new things keeps our minds active, which helps keep old age at bay. We seem to have forgotten the value of this skill, with some people feeling like they no longer are obligated to learn anything once they're out of school, with some people admitting they haven't read a single book since graduating. Granted, the modern school system doesn't exactly encourage the idea that learning new things can being entertaining, but it can be if it's something you're actually interested in.
Vow to learn a few more things. Pick up a new skill, learn a new language, take up a musical instrument. Don't let your mind go soft.
Know Your Limits.
Watson is one of the most easily overshadowed characters in fiction. Despite being both a doctor and a soldier, he is so often reduced to standing around dumbstruck thanks to Sherlock's near-superhuman powers of deduction. This is the reason most Sherlock Holmes adaptations have turned him into a complete buffoon. It's only recently that there's been a massive effort to return Watson back into the intelligent, accomplished surgeon and soldier he was in the stories.
One way this is done is to show him being smarter than Sherlock in a more practical and pragmatic way. In “The Blind Banker,” a vital piece of graffiti only Watson has seen is painted over. Sherlock immediately starts walking Watson through bizarre memory tricks to try to remember what it said… only for Watson to finally tell him he took a photo with his camera phone. In general, Watson frequently ignores Sherlock's more extreme tricks for learning and remembering things and simply puts his trust in cameras and diaries to keep track of things, and so should you.
To put it bluntly, you are not Sherlock, your memory stinks. In general, you should take advantage of outside resources. The most common is to simply start keeping a small notebook handy. Whether your recording big million-dollar ideas to simply keeping your grocery list at hand, it's much better to have important things recorded on paper than to trust it to the vague enigma that is the human mind.
Find Healthy Addictions.
Sherlock is surprisingly abrupt about saying that his habit of solving cases is a substitute for more extreme hobbies. Any time he goes for too long without a case, he starts exhibiting the symptoms of withdrawal, and in “His Last Vow” he states outright that he solves crimes as an alternative to getting high. While he's upfront about this, it's become apparent that John is doing the same thing. John begins the series talking to a therapist and showing severe emotional scars. While it would appear this is the result of trauma he experienced during his military service, it's shown that, in fact, it's the exact opposite. Rather than being scarred by the battlefield, he misses it. That's the reason he's so quick to jump into solving cases with Sherlock, both he and Sherlock are essentially addicted; Sherlock to the intellectual stimulation and showing off, Watson to the thrill of danger.
It shouldn't be surprising, though. Humans are an easily-addicted species. On a base level, it makes sense; an option between something that makes us feel good and something that doesn't is a pretty easy choice, and we'll keep coming back for it. Phrases such as “shopaholic” and “adrenaline junkie” aren't entirely hyperbole; we've learned such things can create similar surges of chemicals in the brain as actual addictive substances. The problem is that people pick up negative problems just as easily as positive ones. Some rehabilitation programs have caught on to this, and have started encouraging patients to not so much “kick” a bad habit as much as “replace” it with a better one, much like Sherlock and John have done.
Bad habits are easy to fall into. Every so often, you should analyze what habits you've fallen into and see if they've started having a negative effect. Especially pay attention to the kind of “soft-core” things that likely won't result in an intervention, but still might be holding you back from your full potential. Spending too much on Starbucks? Too much TV? Try to find better hobbies to replace them with. Doing this can usually make you more productive, save money, and can often make you happier and healthier.
Something compels writers to keep coming back to these characters time and time again. Sherlock is still going strong over 120 years later. Amongst all these different interpretations by different writers at different time periods, each have brought something new to the table. This is just a short list from a single series; pick another one and see what else they can teach you.