In many ways a speech is like an essay. So, if you are writing a speech and you are having trouble, think of writing an essay on fear. If you do this, there are a few important elements to keep in mind.
First, think of a thesis. What do you want to say about fear? Do you want to say that fear is irrational, good, able to be conquered, etc.? Unless you know what you want to say about fear, you will not have a good speech.
Second, once you have decided on a thesis, then think of supporting points. So, if your speech is on the ability to overcome fear, then you will want to say how to overcome it. The better your points are, the better your speech will be. You might say that one way we can overcome fear is by being prepared. Another reason might be thinking of the consequences and how they are not too bad, even if one failed. You get the picture. Think of reasons.
Finally, think of how you want to end your speech. Do you want to make it humorous, serious, challenging? Whatever you decide, recap the main point.