Natasha slides her hands down Daniel's back to his buttocks, which she thinks is amazing. He kisses her again, and she puts her hands on his shoulders to slow them down. She knows that if they keep going, it's just going to make it harder later. She decides they can't kiss anymore.
When Natasha stops the kiss because of "later," it suggests that she isn't fully convinced that Attorney Fitzgerald will be able to help her. She hasn't yet decided to give in to her emotions and trust other people.