Question Regarding Insanity

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Okay, so I started the Insanity workout yesterday. I finished the Fit Test, and felt great. This morning I woke up, ate breakfast, and then tried the Plyometric Cardio Circuit. About halfway in, I had to stop due to extreme exhaustion and ridiculous muscle fatigue. Is it okay that I didn't finish a full Insanity workout? Should I go through the warm-up/stretch and second half later today?

I really want to do this whole program, so I just want to make sure I'm not sabotaging myself right out the gate.