Invest in yourself
“There's one investment that supersedes all others: Invest in yourself. ... Nobody can take away what you've got in yourself—and everybody has potential they haven't used yet. If you can increase your potential 10%, 20% or 30% by enhancing your talents, they can't tax it away. Inflation can't take it from you. You have it the rest of your life.”
~ Warren Buffett
Source: Forbes