Here are a few corrections:

Working too hard is a risk factor for high blood pressure, which can lead to heart attacks and other diseases. People who work more than 50 hours a week are nearly 30 percent more likely to report having high blood pressure than people who work less then full time. For example, my uncle works too hard and suffers from back pain , fatigue and high cholesterol. Additionally, he suspects that a doctor would add high blood pressure to that list. Clearly, working overtime is not great for one’s health.

Working excessively can mask weaknesses (why? how? You need to explain this a little.) These weaknesses may surface too late when they have become very serious and are no longer easily fixed.

Consequently, I hope that in the future people will acknowledge that there is more to life than a career and money. (You haven’t discussed what else there is to life.)

I hope this is of some help. Best of luck.

Everything looks pretty good so far…

If the sentence after “My topic is:” is your Title, make sure you capitalize all the words, except for “and”

You should replace the question mark after friends and place a period.

cholesterol is spelled wrong in your essay.

umm…I don’t mean to be rude or anything, but this doesn’t clearly show that working overtime screwed up your uncle’s health. you gave us some stats, said your uncle works too hard, and his doctor diagnosed him with high cholesterol

to make it more clearer, you should take into account what your uncle’s diet is and if he’s a smoker/drinker. Also, you should ask him about how many hours of sleep he gets for each day he works. We (as in, the readers) also don’t know what type of work he does. Does his job involve hard labor, or does he sit in a desk all day?

the more info you have on this, the better your essay will be.

I hope I help you at least a bit. take care!