How was Rick a sentimentalist in the movie Casablanca?

In "Casablanca," Rick Blaine is portrayed as a sentimentalist through his deep emotional connections to the past, particularly his memories of Ilsa Lund. Despite his exterior of cynicism and detachment, Rick's actions reveal a longing for lost love and nostalgia, especially when he sacrifices his own happiness for Ilsa's future. His willingness to help others, like Victor Laszlo, further underscores his underlying idealism and belief in love and sacrifice, highlighting the tension between his hardened facade and his sentimental nature.