Attitude is paramount. You can look at feedback as an assault on you personally or as a source of learning. You haven't failed until you have given up. Your attitude will determine whether the feedback you get is sugar coated or the blunt truth.
Being humble is necessary to receiving feedback on your homework. Should you be prideful and resistant to constructive criticism, others will not give you honest feedback. Humility helps you to be teachable. As you realize that you have writing weaknesses, you will begin improving already.
Writing is not an activity that is done in isolation. Distribute your drafts and invite comments. You can gain valuable insights from others. Each person's background and skills gives them a different perspective that can enhance what you already have written. Your writing is meant to be read. If your friends and family respond positively to your work, it indicates that you are heading in the right direction.
Grades themselves are a source of feedback. An A+ indicates that your work is quality. A lesser score is an invitation to improve and learn. As with other areas of life, you grow with resistance. Embrace and acknowledge this tutoring and your writing will dramatically improve.