If people have the ability (meaning physically able), there's very little one can do to prevent it. What about the person that is done with being kept alive by drugs? Is it suicide if they stop taking the drugs that are keeping them alive, even if it takes 6 month for them to die?
I'm a follower of Christ and I don't believe anyone should take their own life, but I'm also a realist.
At the age of 17, I watched a close friend come out of his bedroom with a 20 ga shotgun. All of us at the party looked at him when he placed the barrel under his chin and pulled the trigger. The only thing we could think of is he invited us all to his house to watch him die. He could have done this deed at any time but he didn't it his way.
I'm glad I've never experienced such an event in my life where I had considered suicide. I can't fathom how bad something must be perceived as insurmountable that the only option left is suicide. But I have known a few people who have done it. Each time, no one really knew the actual reason.