限りだ is a fixed expression that conveys a strong personal feeling, often in response to a situation. It is similar to saying 'cannot help but feel' or 'extremely' in English. The feeling is subjective and intense, typically negative (e.g., regret, loneliness) but also positive (e.g., joy, gratitude).

This pattern is mostly used in written language or formal speech, not in casual conversation. It sounds a bit literary and emphatic. For example, when you hear good news, you might say 嬉しい限りだ to express that you are truly delighted, but in everyday chat you would more likely just say 本当に嬉しい.

Form the pattern by taking the ます-stem of a verb (the form before ます) and adding 限りだ. For nouns, you need の限りだ, but that is rarer. The most natural and common usage is with emotive verbs like 思う, 感じる, 喜ぶ, 残念に思う, etc.