In regards to advice about how to live, listen to your emotions, stop striving to accomplish an impossible amount of work everyday, stop taking responsibility for everything negative that happens, and learn to do things just because they make you happy.
Also, elementary school me, stop 9/11 from happening, which will kill almost 3,000 people, and start a chain reaction that by 2016 will empower white nationalism, lead to a feeble response to around 400,000 people being killed in Syria, and place the world order on precarious ground. Granted, the chain reaction will also cause the removal of some the world's worst dictators and terrorists, so I'll need to get back to you about what to do next.
Also, short real estate in 2006 and long Apple asap.