"I should like to save the Shire, if I could - though there have been times when I thought the inhabitants too stupid and dull for words, and have felt that an earthquake or an invasion of dragons might be good for them. But I don't feel like that now. I feel that as long as the Shire lies behind, safe and comfortable, I shall find wandering more bearable: I shall know that somewhere there is a firm foothold, even if my feet cannot stand there again."

carrying the world around his neck

"I see no hope of it now. But I've got to do the best I can."

Nightshade: What is a painful truth your character has had to face?

I think there are two actually! That I can think of presently.

The similarities between Gollum and himself. 
Because Frodo has the Ring, he sees the ruin it’s done in Gollum, whom he has taken to calling Smeagol. While I disagree with a lot of some of the ways Frodo is portrayed in the films, I really love in particular when Sam responds fairly cruelly to Smeagol and Frodo berates him for it. He asks him what he knows about it, because he knows, that as Gandalf said, a Ringbearer doesn’t die — he fades. What he was is lost over time, and Gollum is Frodo’s blaring reality of what could happen should he succumb as he did. 

So for both his sake, and for Gollum’s, he says quite honestly, “I want to help him because I have to believe he can come back.”

And he wants to believe that he can come back. Even though ultimately, Frodo does not come back.

That bearing the Ring ultimately means solitude.

Galadriel in the films explains that ultimately the Ring is Frodo’s to bear. The Fellowship may shield him, fight alongside him and help him as best they know how but the burdens — the nightmares, the interaction with Sauron and the terrors of darkness and loss are his alone to see and bear. The deterioration will be on his shoulders alone, as will the fate of the world. Even with companions, Frodo to an extent, is still very much alone, even if he wouldn’t admit it to himself. 

I think he realizes this the most when Boromir attacks him, and he sees that he is carrying something that will hurt normally good people by twisting them. Boromir wasn’t a bad person, and Frodo knew that. So he leaves to try and contain that damage, and go alone — as he tried to do in the beginning of the books. 

There are a few scenes in the Two Towers where Frodo seems to be unable to hear or see much of anything, save Sam’s mouth moving, as if he’s gripped by sheer terror from the Ring and their situation. There’s still a great sense of separation between them, even though Frodo is right beside Sam, not all of Frodo is beside him. 

He’s together and he’s alone, all at once, and that makes things very hard.