I ate one of the Rosh HaShanah seudos at a friend’s house. Amongst other dishes, the friend served a courgette dish. When I began to eat this I tasted that it was really rather sour. I was unhappy about this but did not want to cause discomfort and so I finished the portion. However, I am understandably concerned. The minhag not to consume sour foods and drinks on Rosh HaShanah is because these are said to be an omen for the coming year. I would be grateful if the Rav would give truthful guidance concerning this. Please kindly state the sources.
If you would have been at home and not eat it, that would have been correct, as it is not our minhag to eat sour things during this time of the year. However, since the reason you ate it was not to cause discomfort to your host, therefore your eating it was in order to do chesed with someone else. This should be a siman that you should be zoche to do much chesed this year, and Hashem should do much chesed with you and grant you a shana tova.
משנה ברורה סימן תקפג ס”ק ה “שנה מתוקה – וע”כ יש נמנעים לבשל בר”ה מיני חומץ בארש”ט וכדומה וע”כ האוכלים דגים לסימנא שיפרו וירבו כדגים אין מבשלין אותן בחומץ. והנה כל אלו הענינים עושין הכל לסימן טוב ולכן פשיטא שיזהר מאד שלא יכעוס בימים האלו מלבד גודל האיסור כדי שיהיה לסימן טוב רק יהיה שמח לבו ובטוח בד’ עם התשובה ומעש”ט”: