I believe it refers to the highs and lows of the spiritual journey. The line "I have spoke with the tongue of angels" is thought by many to refer to the practice of "speaking in tongues", a form of usually unintelligible ecstatic speech uttered by Charismatic Christians during moments of intense religious fervour. It is believed this speech is divinely inspired. You probably know that Bono was a member of a Charismatic Christian group, Shalom. The line about holding hands with a devil suggests the opposite pull, not towards the divine but towards the sinful and worldly. The hand-holding suggests physical intimacy, and the pull of temptation.