Living in despair, emotional stink, bitterness, basically yuckiness of any sort has no profit for us whatsoever. Resist it. There are times that you might be dealing with some major stuff and some major heartache but it doesn't have to pull you down permanently. Don't let it. There's too much life waiting for you.
I looked up blood in the original language. And it means, well, blood. But it also can mean violence or violent people. So, if you put this in the verse it gives us another thought: There is no profit in violence and in the more subtle form of violence: manipulation. If we get something through manipulating others it will prove false and shallow. We might get our way but if gotten through force it will end up leaving a nasty taste in your mouth and might in the future haunt your thoughts. And thought-haunting is a rotten thing to deal with.