Wǒ měi cì xiǎng gěi tā xiě xìn, què yòu tíbǐ nán xià.
Every time I want to write her a letter, I can't put pen to paper.
Tips
usage
Common in literary contexts and formal letters. The set phrase 提笔忘字 (tíbǐ wàng zì, 'pick up the pen and forget the character') is now widely used to describe the modern phenomenon of forgetting how to handwrite Chinese after relying on pinyin input.