* I only want to eat breakfast. (That person is easy to satisfy and has no other desires in life except breakfast.)
* He only wanted to see Mable. (The writer probably meant he wanted to see only Mable—and not all the others.)
* I only wanted to mail a letter. (I want to mail only a letter.)
Readers will understand what you mean, but why should they have to figure it out? If you want to write with excellence, you'll use only correctly.
Only is a restrictive word;
Make sure you use it properly.