My Sad Experience...

I remember I worked during the daytime and went to university in the evening, after finishing army service. At that time, I didn't feel tired although it was hard and tiring for most of people. About one year passed. I didn't feel uncomfortable, until a bad thing happened to me. I felt a severe pain in my belly. I went to see a doctor and he said "You should take a rest". However, I didn't listen to him and kept doing my job. Later on, my pain got worse and worse and finally I had to quit my job, and take a long leave from school. I should have accepted the doctor's suggestion and not made myself so fatigued. 
From this experience, I learned a very important thing. That is the value of health. There is nothing more important than health. When you lose your health, you can't buy it back.

*Grammar, and word selection were edited/changed to make it read more fluently (: You did a great job!