How about gifting your friend a personalized couple's therapy session with a licensed psychologist? This unique gift will not only be helpful for the couple but also aligns with your friend's love for psychology. You could also consider a personalized, hand-written journal that includes cognitive-behavioral therapy prompts and exercises that they could do together. Alternatively, you could gift them a book on psychology, such as "The Five Love Languages" by Gary Chapman.
Or you can get her/him a star map with the date of the wedding.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.