Just do it

I have heard a lot of people say that:
If I were a millionaire, I would travel all over the world.
If I won a lot of money, I could find a girlfriend.
If I could speak English very well, I could make a lot of friends from all over the world.
If I graduated the school, I couldn’t study any more. ("couldn't study" implies that you are not able to study--공부할 수 없다)
Suggestion: "I wouldn't have to study anymore."
If I had time, I would learn to play piano.
If my children would grow, I would have many time to do work.  ("Would grow" is awkward. The word time cannot be counted, therefore you would not say "many time.")
Suggestion: If my children were grown, I would have a lot of time to do work.

 
And I have heard some people regret and say that: (not exactly wrong but it is awkward. )

If I have studied hard in school, I would make a lot of money. (Usually, "I" is followed with the word "have." However, when you put it in front of if, you change tense, and it would instead be "If I had ______")
If I had studied hard in school, I would make a lot of money.
If I have worked hard, I would buy a house.
If I had worked hard, I would buy a house.
If I have did exercise every day when I was young, I would be more healthy.
If I had exercised every day when I was young, I would be more healthy.
If I have spent my time with my children, my children would be more happy.
If I had spent my time with my children, my children would be more happy.
If I have eaten less, I could lose my weight. 
If I had eaten less, I would have lost weight. 
If I haven’t have relationship with him, I wouldn’t so sad now.
If I hadn't had  a relationship with him, I wouldn’t be so sad now.

 
STOP TO REGRET! STOP TO COMPLAIN! JUST CHOOSE TO DO IT WHAT YOU WANT! (To say ___하지마  say "Stop ____ing.")

STOP REGRETTING. STOP COMPLAINING.

Not bad at all! These are some really complex grammatical structures! Good job!