In this modern day of computers, you are no longer limited by what you wrote being there for all eternity. In writing that last sentence I made many, many mistakes in spelling and punctuation. I changed them before I pressed 'post'. It's easy to do. A few ideas for you:

- First of all, someone who loves you as much as you love them will not care about spelling or punctuation.
- Second, you are not Shakespeare. This is a good thing as it means that the little things you write for your lovers are not going to be analysed and deconstructed by scholars hundreds of years from now. I mean, the poor man wrote many of what he thought were 'throw away' sonnets for women he was trying to seduce only to have them later considered to be the greatest love poems ever written and therefore torn apart by future generations and used to bore school children.
- Good English use comes with practise. Lots of practise. Read and write as much as you can. Unlike some of my friends (who had English public school education) I learnt my grammar the hard way by reading lots of novels and learning from them then writing lots and having those who were taught the easy way scream at me and point out all the many ways in which I torture the poor, innocent apostrophe. This means that I have an instinctive feel for grammar but cannot tell you what anything is called or why...
- I suggest you also read 'Eats, shoots and leaves' by Lynn Truss. It is an accessible and fun book on grammar rules.
- Never trust the Microsoft Word grammar checker. It is evil and misguided. Well, it used to be anyway. It is feasible they may have improved it to follow rules of grammar that actually apply to English instead of Martian as the old ones did. Nevertheless, never take anything like that at face value - always check with a human who knows what they are talking about.
- And finally, meh. Editors get paid to check spelling and grammar. Why make their lives easier?