What should I do to stop incessant talking and hurting others thoughtlessly? And if I make a covenant with Allah and swear to abandon a trait, then break that covenant, will Allah be angry with me and not accept my repentance?

The cure for excessive talkativeness lies in recalling the danger of the tongue, that Allah is All-Hearing, and that the angels record every word. This should be coupled with constant remembrance of Allah, occupying the tongue with beneficial speech, reading the biographies of the righteous, accompanying good people, striving against one's self, and seeking Allah's help. As for laziness, its cure is by seeking Allah's help, striving against one's self, and remembering the shortness of worldly life and the danger of wasting time. Breaking a covenant with Allah Almighty necessitates an expiation for an oath, and repentance is accepted from every penitent.