If you get things that you desire, there may be unforeseen and unpleasant consequences.('Be careful what you wish for, lest it come true.' and 'Be careful what you wish for; you may receive it.' are also used.)
Be that as it may is an expression which means that, while you are prepared to accept that there is some truth in what the other person has just said, it's not going to change your opinions in any significant manner.
Someone who says they've been around the block a few times is indicating that they have life experience relating to the topic at hand. It is not necessary to discuss the introductory aspects of the topic or give beginner level advice.