I think it's utterly inhumane to imprison a person in life if it's just not working for them. People should have access to different sorts of help. As a society, I think we owe it to each other to give each other every chance to make the best of it. But ultimately, forcing a person to remain alive when they've tried everything that might help and it hasn't helped, and their life remains constant suffering, is akin to torture, in my opinion.
That said, a lot of suicides are impulsive, and when people are prevented from impulsive suicides, they're generally glad for it later. I'm for making suicide difficult. If somebody's feeling suicidal, remove knives, firearms, pills, nooses, etc. If they sustain the feeling long enough to work for it, I think they have the right, but most will change their mind first.