Hope this helps! Keep in mind that my corrections are not perfect.My Life in Basic Math
Math, unless it is the specific course title, is generally left lowercase.
For many years, (the times I have dealt?) dealing with Mathematics has been one of those precious times(doesn't make sense-you need to have "times" match up with something relating to "time" earlier in the sentence) in my life. It has been giving me pain due to the several problems that (I faced? passive voice is inappropriate) need to be encountered; though, there were times that I liked Math so much. (liked and "So much" are very informal phrases)
When I was in (got rid of "my", generally not used) 4th (fourth, not 4th-smaller than 10) grade, Mathematics was my favorite subject since, for me, it was uncomplicated (generally "uncomplicated" is seldomly used). I remember that I could recite easily all the numbers in the multiplication table. I could even perfect (you mean "I could even get perfect scores on.." right?) most of the quizzes our teacher would give. (you could actually shorten this to "most quizzes.") That is why (No comma) Math was one of my all-time favorites back then.
When I was in (No "my") 6th grade, however, the lessons became harder. That time, I had to take notes in my notebook. (Or "It then became necessary for me to take notes.") It seemed that my memorization skills decreased. I could hardly get a perfect score in some of my quizzes, but I never failed (a quiz). Perhaps I was becoming an average student.
When I reached my first year in high school, "I am sad to say" (this is very informal) that out of five quizzes in Math, I could merely pass two. It was my first time (dealing) with complex numbers and the algebra. (simplify it) Almost everything went hard on me (this is very informal). I was even worried whenever the Math examination would get near. I would
By that time, I began to hate Math because of the difficulty of the lessons. I would even prefer to study English over Math (informal, better "prefer English to math). Math, for me in those times, was a nail on my forehead. (what do you mean? this idiom is rare, if existing, in english!) I really had to study hard and drink mugs of coffee ( you might want to take out the part about the coffee) for me to embrace (might want to replace with "understand") the concepts. This case continued until the last day of my junior year in high school.
Currently, Math eventually become (is becoming) easier (even) though I have failed some of the quizzes. It seems that I can master some of the lessons by memorization, but that doesn’t mean that I need not (no "to") take the subject seriously. I always say to (tell) myself to try hard (my best?).
As of the time being, I am striving hard to pass all my quizzes in Math. I know that our Math today, I believe, (either you know or you believe-pick one! :) ) is easier compared to last year’s Math. It is therefore right not to waste the remaining opportunity not only to get a high grade, but also to learn. (this is a bit awkward. how about: It is therefore critical to study hard, not only to get a better grade, but also to learn.)