Can one gloss the doctrine of karma as the claim that we are only
really hurting ourselves?
If the mind has right samadhi (which includes hyper sensitiveness), the mind can realize all bad kamma (be it mental, verbal or physical) is hurting oneself; because the mind can directly feel the bad vibrations of its nasty intentions.
However, for those without right samadhi, such as the common puthujjana (worldling), they must see how bad kamma hurts others.
But when we suffer from everyday pangs of frustration, due to e.g.
frustration with our visual appearance, or lack of wealth (these are
The Buddha in the Sutta Pitaka (at SN 37.30) taught a woman that lacks beautiful visual appearance & wealth will still be accepted by others if she has ethical behaviour (morality). If we have faith in the Buddha of the Sutta Pitaka, we will be confident the most important thing is our ethical behaviour. For example, the Buddha in the Sutta Pitaka taught a woman, despite her genetic physical appearance, will look ugly & deformed when she is angry.
Here, Mallikā, a certain woman, is angry, often irritable. Even over a
trivial remark, she is cross (abhisajjati), shaken, vexed, stubborn,
and shows her temper (byāpajjati), anger and sulkiness. She is not a
giver of food, drinks, cloth, vehicles, garlands, scents, ointments,
beddings, dwelling or lightings, to recluses or brahmins. Furthermore,
she is jealous in her heart; jealous of others‟ receiving gains,
honour, respect, esteem, homage and worship; she is vengeful and holds
grudges. If she falls away (cutā) and returns (āgacchati) to such a
state, wherever she comes forth (paccājāyati), she is ugly, deformed, of
very mean appearance and she is poor, having few things, of little
wealth and little influence.
AN 4.197 clearly shows how angry people hurt themselves.