Feynman summed up my problem here.
"I think that when we know that we actually do live in uncertainty, then we ought to admit it; it is of great value to realize that we do not know the answers to different questions. This attitude of mind – this attitude of uncertainty – is vital to the scientist, and it is this attitude of mind which the student must first acquire. It becomes a habit of thought. Once acquired, one cannot retreat from it any more."
And thus: "The spirit of uncertainty in science is an attitude toward the metaphysical questions that is quite different from the certainty and faith that is demanded in religion."
So instead of 'trying to believe things' I finally gave up and decided to believe only things that I could not disbelieve.
What do I mean by ‘believe’ or ‘disbelieve’? I favour the definition provided by the 19th century American philosopher Charles Sanders Peirce: “A belief is a habit, i.e., a readiness or disposition to respond in certain kind of ways on certain kinds of occasions.”
With this definition, it should become evident that there are some things that cannot be disbelieved. We cannot disbelieve F = GMm/r2, in that we cannot habitually behave as if it were not true: each time we behave as if it were not true, we are likely to injure ourselves, and if we attempt to make it a habit we are sure to break before the universe does.
In the same time as we cannot disbelieve F = GMm/r2, we cannot disbelieve that life is better than death. Believing this, which means acting upon it, we cease to exist.
I think the idea that death is better than life is one of a small number of beliefs that, believed in a Peircean way, will destroy any functioning society, and so collectively cannot be believed. The antithesis of these beliefs is what C. S. Lewis called the “Tao”: the nugget of ethics common to every ethical system we know about.
So now I feel better most of the time and worse some of the time, compared to before Christmas 2007 when I was trying to be both a scientist and a Catholic.