15 successful entrepreneurs share the most important lesson they learned in their 30s

If your 20s are a time for figuring out who you are and what your purpose is, then your 30s are a time for discovering how to turn your aspirations into reality.

We asked entrepreneurs, including billionaire "Shark Tank" investor Mark Cuban and the cofounders of popular retailer Warby Parker, to share the most important lesson they learned in their 30s.

They shared insights into how their worldview and business approach changed with experience and created the success they enjoy today.