Open with a strong first paragraph that quickly goes over the sum of everything good about you. Your desire for the position, required and desirable (especially desirable) skills, and other aspects of yourself that make you worth considering:
I feel I am the best candidate for the position of [BLANK] because [BLANK], etc. I have had experience in [BLANK] by doing [BLANK] and [BLANK], etc. I also [BLANK], which [BLANK] with my [BLANK]. I am [BLANK], [BLANK], and [BLANK]. I have also [BLANK] in the past which [BLANK].
From here go on into more detail about a few of the [BLANK]s you filled in, but nothing too much or over-extensive, just a little more context to provide info on why you're a better candidate.
Don't use enthusiastic when describing yourself, or any other words you feel put you in a positive light but really they're just obvious filler because you couldn't think of other qualities. They know people use those words for this, and they'll ignore them. Use words that actually mean something to the position and show you know what the fuck you're talking about.
I did most of this when I was applying for stuff and I got called back for a fair few interviews, and accidentally got offered two jobs at once. Even if they don't ask for it, this can make a good personal statement if you're good at wording it, and you can pin it to every application you send out.