You're correct that, "I managed the set up of the new server system and am proud of the result," is considered bad form, but your reason is not correct. The only thing incorrect about that sentence from a grammatical standpoint is the change in tense. It would be correct if it read, "I managed the set up of the new server system and was proud of the result," or if it read, "I managed the set up of the new server system, and I am proud of the result." The latter example would probably be better for the resume, but either sentence would be correct.