Because of the fall of man, the world we live in is destine to undermine our trust in God.
Any pleasure from things of this world is only a temporary happiness or security before it passes away.
When we get attached to something not of God fear results and fear stalks us constantly;
the fear of the future, the fear of the unknown.
With God we know the future we know the unknown.
The future is eternal live and the unknown is beatitude (supreme happiness).
Our hearts are made for God. (CCC 27)
Do not be afraid.
Be at peace.