The last time I had to that, I honestly made it up. But, the more I thought about it, the more it did produce actual emotions, so it wasn't a total lie. I entered an art competition last year and the theme was 'Hopes and Dreams'. I do landscapes mainly and didn't want to venture into new territory. So, I picked a good one of a lighthouse, on the Atlantic coast, and spoke about how I dreamed of looking out over a vast majestic ocean, or words to that effect - I wrote a whole paragraph. The more I got into trying to come up with poetic words, the more I actually believed it, I just hadn't thought about it before. Good luck.
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"We act as though comfort and luxury were the chief requirements of life, when all we need to make us really happy is something to be enthusiatic about." Charles Kingsley