I think everyone, suicidal or not, should have a method in place to leave this world in his/her own terms. Be it Nembutal or whatever other method you are at peace with that guarantees you a death as peaceful as possible. It works like any other insurance you can think of ( property, car, life, etc) . In this case, its an insurance against life turning ugly in the future. If life becomes unbearable to you , nobody is going to help you kill yourself. Even if they wanted to , they could face charges. Life is too fragile to not have something in place.
In countries with a high percentage non-religious population its very common to talk openly about reserving your right to leave this life when and how you want. And yet nobody has a method in place because you always speak about in hypothetical terms and you are not taught to do so ( as opposed to you being told to be wise and buy home insurance ) .I think you should do the work, secure the method and forget about it. Just like financial planning, for example.
You are buying yourself options. Even for something as common as cancer. YOu may not want to subject your family to you dying of cancer. Its a very ugly and unpleasent thing to watch and listen to.