This song's for the one I loved, at least that's what I thought. My intent is to raise doubt about whether I love "the one", but I think "at least that's what I thought" could refer to the whole ...
I instinctively translate it "as best as you can", however this makes no sense. What is the real structure behind this phrase? I'll include an Ngram to illustrate the historical presence of this ...
"You bet you"? That's the closest I could think of. Or is it "you bet yourself", with the "self" omitted so it's quicker to say? Or is it something else altogether?