what is the function of (だと) and (一人) in this sentence


the sentence is "もう駄目だと 一人孤独を抱いても".

i took this sentence from this page:

"<http://honyakusitemita.pixnet.net/blog/post/91368550-%5Bblood%2B%EF%BC%88%E8%A1%80%E6%88%B0%EF%BC%89-%E7%89%87%E9%A0%AD%E6%9B%B23%5Duverworld-
color-of-the-heart>", it is a song of uverworld.

i have understood that this sentences means someting like:

"even if it useless, i embrace the solitude", but i don't know what means
exactly.

then, i also don't know what is the function of this(だと), and this (ひとり) in te
sentence.

thanks in advance, guys.

