Why is it so difficult to believe in God's promises?

This is what Isaiah 41:10 and 13 says:

So do not fear, for I am with you; do not be dismayed, for I am your God. I will strengthen you and help you; I will uphold you with my righteous right hand.

and

For I am the LORD, your God, who takes hold of your right hand and says to you, Do not fear; I will help you.

So, God very clearly tells us we have nothing fear, but I'm finding it very difficult to believe it as I'm trying to obey what God has asked me to do. It seems it is really much easier to focus on things going around me than it is to focus on who God is and what He says.

In other news: I still haven't heard anything concrete from the Kindergarten. My contract ends in 6 weeks and I have no idea what I will do after. Well, ok, I do have some idea, but no idea how it will actually work out. I'm getting a tax adviser to sort out my taxes and to get me a tax number. I just hope I can actually meet him soon! Every time I've made an appointment with him, I've been given a class!! AAAARGH! It's very hard to trust God and not be afraid...