I long for the magnificent improvements in my English
I want to make great strides improving my English.<<I think this more natural. The way you wrote it is fine, but it sounds like it is from a poem! :)
I feel that my English is not good enough.
I don't think my English is good enough.<<again, this is just more natural sounding. But what you wrote is OK too.
Maybe it is a the result of a lacking of time in spent learning English or poor self-discipline. However,as a the saying goes "no sweet without sweat".
I can only make it on the ground that improve a lot if I spend more time on learning English learning and if I have a strong will power. Besides, I need a sound time good schedule is needed,which that can help me make full use of my leisure time.
In addition, I've made a the decision that I will to try hard to write an essay every day online if time permits and if all my work is done. Keep fighting!
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Try your best! Keep writing! :D