[link to original on tumblr]
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Near the end in the original recording, there's a weird rhythmic change in the guitar part. I don't know whether it's supposed to be like that or if Paul Atkinson forgot that the progression at the end is repeated. In any case, I didn't include that.
"I Don't Want to Worry" also exhibits the whole start-a-diatonic-descent-in-the-bass-via-a-7th-chord that I've talked about before. I'm not sure about "Celebration" or "Christmas for the Free" because Argent and White were sharing the writing credits by then, but the other songs I've found this in are Rod Argent songs - "She's Coming Home" and (to some degree) "I Want Her She Wants Me." "I Don't Want to Worry" is a Chris White song though, which makes the occurrence of that feature even more interesting.
It occurs during the second half of the verses (or maybe it's the beginning of the choruses). Whatever it's called, it's the part with "It seems to me / We used to be / So happy now." Interestingly, that diatonic line is broken off when the lyrics get to "It worries me." Instead of continuing the D C# B phrase to an A, it goes to an E.