I would:<p>- describe all the ailments I experienced with age and then teach myself how to mitigate all those things through proper nutrition, exercise and sleep.<p>- teach myself about personal relationships, something I missed in my youth and had to learn the hard ways.<p>- describe all the shenanigans I experienced in the early dot-com days and make myself even more fearless early on.<p>- teach myself to research company founders and pick companies to work for based on the previous experience they had building successful organizations.<p>- say, "Don't open that, it's a trap!" <i>inside joke that only I would get</i>