"Hast no stomach for" refers to the lack of willingness or courage to undertake a particular task or activity. Antonyms for this phrase could include "eager", "willing", "enthusiastic", "bold", "daring", "adventurous", "persevering", "resolute", "determined", "courageous" and "fearless". These words indicate a strong desire to tackle challenges and a willingness to take risks. Such attributes are essential for achieving success in life and overcoming obstacles. Therefore, it is important to cultivate the optimism and determination to surmount challenges instead of being dispirited by them.