One simple way to make sure your speech builds towards an interesting, exciting ending is to create a speech graph. Graph out how you would like your speech to look:
And then work to develop this sort of a "feel" in your speech. Where your speech should be moving upward, pick up the energy, excitement, and pace of the speech. where your speech has a moment of moving downward, take off some of the energy, excitement, and pace. If your speech has a moment where it moves sharply downward, use a serious, slow, steady pacing of the voice.
Graphing it out,
Tim