You tackle many of the destructive myths about suicide. However it is also a myth to think it is entirely preventable.
Relentless severe depression has, a potential for suicide, despite the best of interventions, the love and empathy of family and friends, and the investment in living of the sufferer, suicide happens.
You intimate that it is a matter of untapped "strength." To say that it is preventable is to "blame" the victims, intimating that what was done wasn't correct or enough. This adds to the already considerable suffering of survivors.
As someone who was profoundly depressed enough to see suicide as a reasonable possibility, I know the relentless power it exerts. I believe that every life is worth grabbing hold of to try to sustain. The horrific number of suicides can be drastically reduced with changes in attitudes and behavior.
However, the vicims of suicide and their loved ones deserve the recognition that sometimes suicide is a casualty of a serious illness. and not a function of what could have been done to prevent it.