How to develop fortitude? Specifically when someone you love or whose opinion matters to you greatly attacks your way of life, your beliefs, or even on a smaller scale just makes you feel ignored, pushed around, etc.
I find I quickly lose confidence in my &quot;inner voice&quot; when my loved ones, particularly family, do this. Generally when a stranger does this to me it's easier to let go.
Does anyone have a useful visual metaphor or story around this? I try to see myself as a rock and their words like arrows pinging off me but it doesn't work.
Perhaps it is possible that you aren't confident in being right, perhaps you are wrong and people who are challenging your views are right. In that case you should figure it out and do as they say if they are right and do as you see fit if you are right. Whether you are or aren't is the most important factor in determining your course of action.
If you aren't certain then don't get into a discussion. In general avoid getting into a debate if you aren't certain in your righteousness and don't understand the opposing position better than the opposition does.
You can always say 'this is my conviction but i am not certain, if you have all the answers then teach me but if you are likewise of speculative persuation then let's set this discussion aside until one of us gains verified confidence'. It will solve your problem because this statement protects the truth and avoids arguments.

But to what extent, Master Gotama, is there the safeguarding of the truth? To what extent does one safeguard the truth? We ask Master Gotama about the safeguarding of the truth.&quot;
&quot;If a person has conviction, his statement, 'This is my conviction,' safeguards the truth. But he doesn't yet come to the definite conclusion that 'Only this is true; anything else is worthless.' To this extent, Bharadvaja, there is the safeguarding of the truth. To this extent one safeguards the truth. I describe this as the safeguarding of the truth. But it is not yet an awakening to the truth.
&quot;If a person likes something... holds an unbroken tradition... has something reasoned through analogy... has something he agrees to, having pondered views, his statement, 'This is what I agree to, having pondered views,' safeguards the truth. But he doesn't yet come to the definite conclusion that 'Only this is true; anything else is worthless.' To this extent, Bharadvaja, there is the safeguarding of the truth. To this extent one safeguards the truth. I describe this as the safeguarding of the truth. But it is not yet an awakening to the truth. https://www.accesstoinsight.org/tipitaka/mn/mn.095x.than.html

As to how one develops fortitude there is no simple answer but this very training does develop it, namely the four bases of mindfulness, five faculties, five bases of power, seven factors of awakening, this noble eightfold path. One should avoid associating with bullies and seclude oneself from abusive people until becoming such that one's forbearance is one's mighty army and one can endure both the abuse and one's own anger without letting it loose.
When it comes to parents we can't just go along with whatever they say because we owe them

I tell you, monks, there are two people who are not easy to repay. Which two? Your mother &amp; father. Even if you were to carry your mother on one shoulder &amp; your father on the other shoulder for 100 years, and were to look after them by anointing, massaging, bathing, &amp; rubbing their limbs, and they were to defecate &amp; urinate right there [on your shoulders], you would not in that way pay or repay your parents. If you were to establish your mother &amp; father in absolute sovereignty over this great earth, abounding in the seven treasures, you would not in that way pay or repay your parents. Why is that? Mother &amp; father do much for their children. They care for them, they nourish them, they introduce them to this world. But anyone who rouses his unbelieving mother &amp; father, settles &amp; establishes them in conviction; rouses his unvirtuous mother &amp; father, settles &amp; establishes them in virtue; rouses his stingy mother &amp; father, settles &amp; establishes them in generosity; rouses his foolish mother &amp; father, settles &amp; establishes them in discernment: To this extent one pays &amp; repays one's mother &amp; father.&quot;

It is normal that we want to bring people we like along with us and be aligned in view but we should associate with our equals or better and a person is neither of those by the virtue of kinship alone. Therefore it is entirely reasonable to seclude oneself and to that extent violate even kinship.
It is just sad to associate with people of different persuation because it is unpleasant to watch people we care about aim down and furthermore listening to their rationalization for doing so. If we don't agree with their rationalization a person will usually get upset and defensive about it. Therefore best leave them to their own until you have an ace in your sleeve so to speak.
Don't waste words of wisdom on people who are fixated in wrong views, don't throw pearls before swine.

There is no companionship with fools. Living with fools is painful as living with foes.

As to how to train in more detail, look up development of perceptions &amp; contemplation, learn the defining of elements and practise jhana. .
If you are going to contemplate whilst people are abusing you then there are better themes:
I have compiled ~ 20 to be developed lines of reasoning and visualizations here (theravadin texts, mostly sutta):
https://docs.google.com/document/d/1kZxstsAvjhj9Svc47RUKRIyKQMuHMD4adIvr_7pp2uI/edit?usp=drivesdk
Something you should reflect on often is that people are like that. They critcized even the Buddha. Another thing is that bad people don't like good people.

Should one see a wise man,
Who, like a revealer of treasures,
Points out faults and reproves,
Let one associate with such a one,
Well is it, not ill, to associate with such a one.
Let him admonish, exhort,
And shield from wrong.
Truly, pleasing is he to the good,
Displeasing is he to the bad.
Associate not with evil friends;
Associate not with mean men;
Associate with good friend;
Associate with noble men.