Writing Feedback / Effects of Working and Studying at the Same Time [4]

You have to be careful with your use of tenses and your sentence formation. I corrected this section to show you things you missed out when you were proof reading so just be careful and you'll be fine.

Doing this every single day will harm their health and their brain. Lack of sleep is the major cause of heart disease and high blood pressure. It kills the mood too. Working students will be have bad headaches and be tired all the time. They will be have bad moods even when they talk to their families and friends. Lack of sleep impairs attention and thinking. Plus working students will not be able to comprehend easily. They be in bad moods all the time, under stress, and in extremely bad health.

The most important thing in life we have is time: without maintaining it, life will not exist. Studying and working at the same time will burn your time and will make you busy all the time, to the point you will not feel yourself living.It is complicated to control school and work,you may just end up failing in both.

That's how I would write it.