What does the maxim: "All is in the hands of heaven; except the fear of heaven." mean?

what a beautiful question!

It is a Jewish proverb and it means that there is only one power,

the power of love and bestowal.

The only choice one has is to either believe

and have a relationship with the creator or not.

It is a very complicated subject

and I found these sources very useful.

You might find them useful too.

Good luck!

The maxim: "All is in the hands of heaven; except the fear of heaven." was said in Talmud (The Talmud is a central text of mainstream Judaism.)

It means,

God runs everything except whether people obey him! This phrase for obedience, or worship, or piety strikes us as unusual – is fear really an ideal relationship? In a world where human power to control life and death was minimal and the caprices of disease, disaster, and fate were great, perhaps such a reaction was natural. Today, however, life is too precious a commodity to live it in fear – let us live in joy instead.