"With all the rehearsing I'm doing, something has to go, and I'm afraid that's the one."
I can't understand the meaning of the phrase at all.
Without more context it is not possible to be completely certain what this person is talking about. However, most probably "something has to go" means that the speaker has to give up some activity because he/she does not have enough time for it in addition to doing the rehearsing. "that's the one" probably means that some thing previously mentioned is the said activity.
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Without more context it is not possible to be completely certain what this person is talking about. However, most probably "something has to go" means that the speaker has to give up some activity because he/she does not have enough time for it in addition to doing the rehearsing. "that's the one" probably means that some thing previously mentioned is the said activity.