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.)
(USA) To be out in left field is not to know what's going on. Taken from baseball, when youngsters assign less capable players to the outfield where the ball is less likely to be hit by a young player. In business, one might say, 'Don't ask the new manager; he's out in left field and doesn't know any answers yet.'
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.
Something someone says when they want to get out of a place or situation, meaning 'Get me out of here!'.
(It comes from the TV series and movies Star Trek, though the exact words used were a little different.)
(USA) If someone is trying to convince people to do or feel something without any hope of succeeding, they're beating a dead horse.
This is used when someone is trying to raise interest in an issue that no-one supports anymore; beating a dead horse will not make it do any more work.
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.
A belief in the hereafter is a belief in the afterlife, or life after death. It is, therefore, associated with religions and the soul's journey to heaven or to hell, whichever way being just deserts for the person based on how they led their life.