Can you tell me one lesson you learned in the last year?

I just want to specify very recent one, In my current project, we encountered most challenging issue was without getting authorised inputs from the client we started the design. The design almost completed and than we received signed documents which is more clear and 50% design to re work again. Still client only asked us to start the design with available documents at the initial stage, but we lost the booking hours due to this issue. Hence, we as a team had a meeting and discussed this issue and make a note to avoid this type of repetative works, design should be started once the input documents are signed and approved from client.