"if" and "but".. are they relevant..?

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Many times we hear people using these words.."if" and "but" to convey their views on any matter.For instance "if I had known the problem earlier I would have solved it without any difficulty".Similarly "but for his ill health he could have participated" Like this we hear these two words being used several times to express the other side of anything.They are only ideas or possibilities which have not been materialized or happened.Can they be rectified or corrected?NO.They refer to things happened already and not things which are going to happen.It is only wishful thinking. I wonder as to how far they are relevant to the present.Can you tell me..?