This question is difficult to answer because different people have different personalities and expressions, so it is difficult to determine how to say it without sounding casual. However, you can refer to the following suggestions: 1. Express your thoughts and feelings honestly and directly. You can say,"I'm very grateful that you have feelings for me, but I don't want to just randomly find a partner. I hope that we can get to know each other first and see if we're suitable as each other's partners." 2. Express gratitude and respect. When a guy expressed his love to you, you should first express your gratitude and let him know that you respect his decision. You could say," Thank you for your good impression of me. I appreciate your attention. However, I still need time to think about my feelings and thoughts." 3. Maintain confidence and independence. Even if you have a good impression of this person, remember to maintain your confidence and independence. Don't let the other party's expression affect your emotions and attitude. You can say,"I appreciate your opinion of me, but I think I need time to think about it." I hope you can respect my decision and let's continue to understand each other." The most important thing was to maintain sincerity and confidence. Don't feel uneasy because of the other person's expression. Instead, express your thoughts and feelings with a sincere attitude and confident language.