"Closing doors" would be an antonym for the phrase "opening doors." While opening doors represents opportunities and new beginnings, closing doors are symbolic of missed chances and dead ends. Sometimes, closing doors is necessary to move forward and make progress. Other times, it can be disappointing and heartbreaking. However, it is essential to remember that closing doors does not signify the end of everything. It can also mean the beginning of something else, such as a new chapter, a different path, or a fresh start. Learning to embrace both opening and closing doors is key to personal and professional growth.