I've been reading Michael Grant's The Twelve Caesars, a history of the first 12 Roman Emperors, starting with Julius Caesar.
One of Grant's observations is the old saw that power corrupts. Figures such as Nero and Vitellius used the resources of the Empire to satisfy their own personal desires (which could be pretty deviant at times!). It's not hard to jump from Vitellius' absurdly expensive feasts to Dennis Koslowski's $10,000 umbrella holders. In fact, it's easy to see that human nature and psychology hasn't changed in 2000 years. Scrub off the Latin names, and it's hard to tell that Grant isn't talking about modern-day politics.
More useful, at least in my mind, are the patterns that emerge in terms of the emperors' rise and fall. Each emperor attained the purple by cultivating a power base, generally the army or Praetorian Guard. Those that survived maintained their power base and reached out to other influencers like the Senate. The less successful, like the unfortunate Galba, who lasted less than a year after replacing Nero, neglected their power base and were quickly deposed. In Galba's case, he made the suicidal move of breaking a promise to pay bonuses to the Praetorian Guard that had brough him to power.
We may live in a different time, and my goals (making the various projects I'm involved with more successful) may be more modest that ruling a globe-spanning empire, but all of the same lessons apply.