When you join to independent clauses with a conjunction you stablishes the equality in this clauses, however in this case you can see that the clauses have a causal relation, it could be said If you don’t hold my hand, I will drown, in this case the best conjunction to put the clauses together is “or” “Hold my hand or I will drown.”
You’ve heard people mention that when they woke up in a good mood from a good night’s sleep, they noticed the sun was shining, the sky was blue, the birds were singing, and things were looking good with regard to a sense of optimism, right? These are all symbolic of hope—sun shining/blue skies/birds singing. If we look at this excerpt, the same sense of hope can be seen in the lines:
“The notes of a distant song which someone was singing reached her faintly, and countless sparrows were twittering in the eaves. There were patches of blue sky showing here and there through the clouds that had met and piled one above the other in the west facing her window.”