There are many possibilities. Judging from the surface meaning of the word, it should be addressed to someone. I hope your eyes can only see a smile, which means that someone will see something other than a smile, such as sadness and sadness. The person who wrote this sentence hopes that someone will only see the bright side of the smile, which shows that someone's position in her heart should be very important and will also cause him worry. If he said to himself, it is possible that people can be ruthless, unless they are familiar with every grass and tree, so can girls.