How in the world do I write a personal statement under 250 words?

I would definitely stick to keeping within the number of words allowed. You don't want to stick out like a sore thumb, and show that you can't follow directions! You don't want them to disqualify you or look down on you for not following the word count. Just try your best, I'm sure it's hard for all the applicants :)

Exceed 250 words. Then simplify it with shorter, more direct statements. Then if it still exceeds, rinse and repeat. For a final check, go over it.

TL;DR

Summarize.

^see what i did there?

For a conference i had an abstract, 500 words. The same project for cn3 promotion, I had to butcher it to 120. As the previous poster stated, go ahead and write your statement and then strip down all the fluff cause really, 300 words is a lot. No one is really all that interested in reading about you.

I had a similar problem when applying to my nursing program. Ours had to be a page or less, mine was 2 when I first wrote it. Go through and really defluff it. Often, we write things repetitively and do not realize it. What sets you apart from the other nursing applicants? What makes YOU stand out? Focus on those. I also had a few friends read through it and see what they noticed when reading through it. My friends caught a couple of sentences that seemed to say the same thing in other words.

I had to write a 100 word maximum essay for my application. Advice from my english professor at the time was to jump right to the point. Leave out things like "I've always wanted to be a nurse because....blah blah blah" and things like "I would be a good nurse because I'm compassionate, etc". The board gets hundreds of applications that start off like this. Instead, jump right in and focus on what sets you apart. Ex: I would make a good nurse because I come from a non-traditional family and was raised by a single mother. Boom, you catch their attention. Then you could go into how that has shaped you and made you a good candidate for nursing. That's just the example that I used because mine was about how I would diversify nursing, and I decided I would do so by setting up a scholarship fund for non-traditional youth interested in nursing.