write a story with idioms I learned today. -thanks for anyone who is willing to correct me!

Nice job. Its good to practice using idioms like this, but in normal writing or speaking you don't want to use too many, it can make you sound awkward and unnatural. 

Mr. X saved me in the 11th hour. If it wasn't for him, I'd be a dead body. I was doing cross words this morning to kill some time, and totally forgot about the stew in the kitchen. The flame had somehow gone out and gas was leaking, which made me feel sleepy. I'd like to catch 40 winks, I was thinking. In the nick of time, I heard someone knocking at the door. It turned out to be Mr. X, who visits me once in a blue moon. As I heard him knocking, I couldn't answer it...

I want to develop good habits

Hi. Nice job! I rewrote it to make it sound more natural. Many of the things I changed weren't really wrong, they just sounded a bit awkward. There are some parts that are a little vague, and it would be easier to understand your meaning if you included more information. Good job and keep studying!

I have many bad habits, like staying up too late at night and playing games on my cell phone and computer. It sucks because it wastes a lot of time that I could be using to better myself. Today I thought of something strange and almost did it, but finally I came to my sense and quit. (This sentence is a little vague, it would be better if you could describe what that thing was) This meant a lot to me because it was the first time that I tried to beat the evil in my mind and won. I'm starting to believe that I can be a better person in the future if I can stick to it. 

Haven't Written Diaries for a While

Nice job. Reading A Dream of Red Mansions seems like a big project. I'm not sure if I would have to patience to do it. haha. I rewrote the passage and changed a few small things to make it sound more natural:

This Monday marked the beginning of summer. I had planned to finish reading A Dream of Red Mansions before summer and I did it. I think spring is the best season to read this book. Four of the main female characters have "春“ (the character for spring) in their names, and at the end of the book all of them are either dead or forced to move far away from home. The "end of spring" represents the end of the once prosperous family. While reading the book, I always pitted the women who had no rights in their feudal society. Although  I was always moved by the love story, but the book is so much more than that. It reflects the power struggle in the royal court during the Qing Dynasty, which was also very intriguing to me. If you want to understand the metaphors behind the words, you need to do a lot of research, so reading a masterpiece like this is as much torment as it is enjoyment. Spring is gone and summer is here. Now I need to prepare for an important exam, which is not at all enjoyable, but very useful. 

Confused mood

Your writing was clear and easy to understand, I rewrote it just  to make it sound a little more natural: 

I feel like my life isn't very fulfilling. I've always wanted to get better at English, but I'm not sure how to go about it. It makes me confused every day, and I'm afraid I will keep feeling like this. Should I make a plan? I'm not sure where to start and I rely heavily on translation tools. Its past midnight in China and I need to go to bed because I have to go to work tomorrow. Good night everyone. I hope that when I wake up in the morning and long into Italki I can see some suggestions on how to study  from you. If my writing has any mistakes I hope you can tell me. Finally, have a nice day. 

Its very difficult to go back to learning again once you are out of the habit. Especially if you are busy with work. My advice would be to start small, don't give yourself a lot of pressure. Pick a simple goal, like reading a news article everyday, or writing a paragraph in a journal every day. Once you get back into the habit of studying it will get easier and easier. Make sure you enjoy the process. The key is doing a little bit every day, and having fun doing it. Good luck!