-suicide doesn't end the pain, it passes it on to others (I don't think this is the correct wording but oh well)
This prompts the question: why are suicidal people responsible for the feelings of others? I am not saying that I believe this rhetorical question to be true, necessarily, but this is something to think about because it is the other side of the argument that many with an anti-choice stance do not consider. Given that we are told to take ownership of our own happiness, and to not blame others for our sorrow, it then seems hypocritical for the anti-choice crowd or society as a whole to then offload their grief and pain onto somebody who has ended their life, as if they are suddenly in control of everybody elses emotions - despite always being told otherwise.
Happiness does not always equate to being comfortable (not suffering) in life, or having your basic and important needs meat. Also happiness needs to be better defined, because everybody has their take on it, but certain perceptions of happiness are damaging. For example some individuals think being "happy" means suppressing negative thoughts, and putting on a struggling smile while saying
"I'm fine!" - even when you are clearly not okay. This contributes to the stigma of opening up about your feelings which, in turn, can lead to suicide.
Peoples situations do not always get better; a person who is terminally ill who spends the last few months of their lives writhing in agony, or the countless homeless and impoverished who are swept under the rug because they are viewed by some as an inconvenience. These are just two examples, out of so many, were somebodies situation does not get better. The world is not a fairytale. Not everyone gets to marry the prince/princess and live "happily ever after". There are so many variables in this existence that make it impossible (from our current understanding) to be completely free of cruelty - which is horrible.
I do not believe that the platitudes you have mentioned can be argued against easily. They are repeated so many times that not many actually stop to question whether or not they are true; they are seen as facts just because everybody else repeats them. All that you can do is try to make reasonable arguments against them; then others will either see your point, or they will not. The stigma surrounding suicide is concrete and it is likely that it will only diminish slowly and gradually over time, as more and more individuals are exposed to the insanity that we call reality.