What we see in the second sentence of the example is an actual run-on sentence: a sentence that lacks even a misused comma to slow the headlong rush. It needs either a period or a semicolon after friend.
Lives are countable. Replace amount (for uncountable nouns) with number. (If you really, really want to use the word amount for some reason, change the sentence to say unlimited amount of life; lives are countable, but life is not.)
Unless used as a proper name (for a person or anything else), amber should not be capitalized.
The last sentence is compound and needs a comma after room.
“This is going to be horrible. Pain is your friend; it means you haven’t lost your mind. […] You have an umlimited number of lives in this game. Stay focused on finding that amber room, and no matter what happens, you stand back up each time you fall.”