Diary Mar 7 2014

I didn't realized that time was slipping away.
I didn't realize that time was slipping away.

It is only when it's too late for me to study easily that I realize the importance of self-improvement.
It was only when it was too late for me to study easily that I realized the importance of self-improvement.

It's been more than 10 months since I took my last TOEFL exam, which turned out to be a fiasco.
Good

I still remember that I was planing to take a second time in 2 months right after I walked out of the school gate-- exam venue.
I still remember that I was planning to take it a second time 2 months later, right after I walked out of the school gate.

Ironically, it's been 10 months already.
Good

During this long period of time, honestly I haven't made a big headway and I have been just moving forward at a very slow pace.
During this long period of time, I honestly haven't made much headway and I have just been moving forward at a very slow pace.

I kept wasting time and didn't focus on my desired goal. What is my desired goal?
Good (by which I mean correct, not good that you wasted time and didn't focus on your goal)

Hope this helped, your English is very good, just a couple of issues with past/present tense as well as sounding more natural.