The cottage in Maine
The cottage in Maine is symbolic of a respite for all of the characters. After a long year of intense work and other trials and tribulations, Harriet, Wyn, and the rest of the characters, go to the cabin to recharge. It is a peaceful, restful place; they look forward to going there.
Alcohol
Alcohol is a powerful symbol of pent-up emotion. After Harriet and Wyn imbibe in perhaps too much alcohol, their true feelings about each other come to light. After their argument, they confess that they still love each other and say they felt they couldn't come out and say it. Alcohol also leads to them reconciling.
Medicine
For Harriet, practicing medicine (and becoming a doctor) is symbolic of her prison. For much of her life, her family encouraged her to become a doctor. However, as she discovered more about herself and what she wanted out of her life, she discovered pottery. Medicine makes her feel constricted; pottery makes Harriet seem free.
Societal expectations
Happy Place is an allegory warning against allowing other people to dictate your path and relationships in life. Because of outside pressure, Harriet becomes a doctor. And because of outside pressure, she starts a relationship with Wyn. It is only after she looks at her career path through her own eyes that she becomes more free and fulfilled.
