I have always tried to spell carefully, and have also found myself "insulted" since grade school over poor spelling.
However, having a child with dyslexia and seeing the struggle to spell has given me a new outlook. It has taught me not to be such an uptight and judgemental person about it! I am changing my viewpoint and it is due to compassion and understanding that the written word is to communicate ideas. It's not right to judge a person's intellect based upon proper spelling. It is very wrong and self-righteous of me to that. It's all about compassion and attitude.
When my child is in college, I will treasure any letter, no matter how poorly written!