Have you ever had an invaluable experience in your life? What was it?

yes , i had been before 4 years  .

i entered   the military  during two years ,that time i  gain  invaluable experience

Many.

Too many to name. 
Don't believe what people tell you in bars, is good advice.
If something sounds too good to be true, it usually is, is good to remember.

Having a massive mental breakdown was invaluable because I had to rebuild my brain, and undo damage and terrible thought processes, which now work well and make me stronger. So that one, as painful as it was, was the most important.

Also getting hurt in love, taught me that love is like gambling, as I said to my friend the other day, "never gamble with more than you're willing to lose".

Ego, I've been egotistical in the past, and every time I was, it destroyed every good thing that I had, so it's good to learn that what you take for granted can be taken away from you.

Don't part ways with someone on an arguement, say you'll work it out.

If you have something to give someone, or tell someone, do it because it's not very nice when they die before you get to do/say it.

 If you have ideas or plans, do them, begin; they often work, but your brain tells you they won't, to stop you from feeling bad if they fail. The way you're guaranteed to fail is to never try in the first place. 

Change is not only possible, it's inevitable. 

Any more of my experience and I'll charge :)

All the things you said is definitely invaluable. what makes me think about more was "If you have something to give someone, or tell someone, do it because it's not very nice when they die before you get to do/say it."

I know what you mean, Craig. Losing a friend is an awful experience, of course.

Oh, she was a good woman. I think, these days we hardly find someone heping us and never turn her/him back on us. But, you are so kind like her, and always help me by correcting my notes and answering my questions. :)

Many many thanks to you, Craig.

And I'm so sorry to hear that. May she rest in peace. she seemed to be so kind-hearted, and I know that you loved her so much. I am truly sorry for your loss, Craig.