A simple statement, but I'm smiling as I write this because like many, I've made a lot of mistakes. It's easy to forget looking at those who are successful that there's a story behind the success. That there's an experience and a lesson learned or two.
Fail often, fail early and fail cheaply
Fail = "Try, Learn, Change"
Fail =/= "Failure"
Make a lot of mistakes and learn from them. Incorporate the learnings so that you improve what you're doing. Always be improving.
Make your mistakes as early as possible. Don't wait until the last minute to learn that you've failed and didn't have enough time to make corrections.
Don't buy a car or (insert other expensive items here) that you don't like. Failing does not have to be expensive to have great learnings. Try things before going all out. See if you like a sport before committing to purchasing all the equipment. Prototype business ideas on a small scale to see if they work.
Companies have repeated this mistake countless times. Many have implemented complete products and services only to find out that there wasn't a demand for them.
Expensive lessons are just that. Expensive lessons.