Please explain the following lines from "If" by Rudyard Kipling.if you can trust yourself when all men doubt you but make allowances for their doubting too
In the poem 'If' by Rudyard Kipling, the poet is not only advising his son but sending out the message to other readers too, including us. He is advising us to have 'the courage of our convictions' in many situations. However, first we must know we are right, or have a strong suspicion. Kipling is saying that we should not dismiss the doubts of others out of hand, but consider them well in making our final decision. Once we are sure we have done enough research and taken enough advice and opininions and still feel the same about our decision - then we should be courageous and trust our instincts. We should 'make allowances' by not punishing those who are 'wrong' in our opinion, for doing so might render them less likely to proffer an opinion next time.
This whole poem is about how the speaker wants his son to act so that his son can truly be a "man." The basic idea is that the son has to be able to function well in all situations and deal with all different kinds of people. The son has to be in complete control of himself all the time.
The quote you cite refers to these ideas. The first part of the quote means that the son must never doubt himself. When other people doubt him, he must remain sure of what he is doing.
But, at the same time, he cannot be too arrogant towards those other people. He has to realize that they might not be as good as he is and so he has to sort of forgive them (make allowances) for doubting him.