Meyasu (目安 - Rough Standard)

I write short English texts every day on Lang-8 while defining 100 words as 'meyasu' (目安).

Meyasu means goals, rough standards, or rough indications.

This word is a noun form of the adjective 'meyasushi' (目安し), which was used in the Heian period.

Me (目) means 'eye' and yasushi (安し) means 'to feel relieved,' so the combination means "to feel relieved to see something" or "something is easy to see."

In the Kamakura period, what you can understand if you see, such as a scale, came to be called meyasu, and it has come to mean its current meanings.

私は毎日、100単語を「目安」にLang-8で記事を投稿しています。

「目安」とは、目標やおおよその基準、おおよその見当などを意味する言葉です。

この言葉は、平安時代に使われていた「目安し」という形容詞が名詞化したものです。

「目」は 'eye,' 「安し」は 'to feel relieved' を意味するので、「目安し」は "to feel relieved to see something" もしくは "something is easy to see" を意味します。

そして鎌倉時代、目盛りなど見てすぐにわかるものを「目安」と呼ぶようになり、現在の「目標」や「基準」などの意味を持つようになりました。

• I write short English texts every day on Lang-8 while defining 100 words as 'meyasu' (目安).
• As 'meyasu' (目安), I write short English texts every day on Lang-8 while defining 100 words as 'meyasu' (目安).

  If you put this at the end, it feels like "as meyasu" only applies to the 100 words. Since meyasu is for both the writing and the defining, it works better at the front.

• Meyasu means goals, rough standards, or rough indications.
• Meyasu means goals, rough standards, or rough indications.

  Instead of indications I might use "criteria" here.

• This word is a noun form of the adjective 'meyasushi' (目安し), which was used in the Heian period.
• This sentence is perfect! No correction needed!

• Me (目) means 'eye' and yasushi (安し) means 'to feel relieved,' so the combination means "to feel relieved to see something" or "something is easy to see."
• This sentence is perfect! No correction needed!

• In the Kamakura period, what you can understand if you see, such as a scale, came to be called meyasu, and it has come to mean its current meanings.
• In the Kamakura period, something one could easily understand just by looking at it, such as a scale, came to be called 'meyasu.' From that, its current meanings evolved/developed/came about.

  This is a complicated sentence in both Japanese and English. There is no doubt a way to keep it as a single sentence, but without restructuring it more completely, it seemed easiest to just split it into 2 sentences in English.
  
  "...it has come to have (mean) its current meanings." mean and meaning don't work well together since they have the same base word. You can keep your same structure and replace with "have".

In the case of your Lang-8 writing and 100 definitions meyasu, I think "daily goals/targets" would be the most natural translation.

Related expressions:

go for/aim for/strive for/pursue one's daily goals/targets
hit/make/achieve/surpass one's daily goals/targets
miss/fail to hit one's daily goals/targets

Ex.
I keep a list of my daily language learning goals on my fridge so that I won't forget them. Every day, I try to hit my target of 100 definitions and at least 1 post on Lang-8. Most days, I make my goals, but even when I miss, I'm happy as long as I can make some effort.

目安という言葉が存在するのが初めて知りました。説明がありがたいですね。自分の言語の目安を書いておかなくて、頭にあるだけですけど。だから、はっきり毎日したいことがわかりません。たぶん、基本の目安を書いておけばいいですね。それをヒットしたらベースです。その以外The cherry on topかThe icing on the cakeになるでしょう。

• I write short English texts every day on Lang-8 while defining 100 words as 'meyasu' (目安).
• I write short English texts every day on Lang-8 while defining 100 words as with a 'meyasu' (目安) of 100 words.

• Meyasu means goals, rough standards, or rough indications.
• Meyasu means goals, rough standards, or rough indications markers.

• In the Kamakura period, what you can understand if you see, such as a scale, came to be called meyasu, and it has come to mean its current meanings.
• In the Kamakura period, what you can understand by if you seeing, such as the marks on a scale, came to be called meyasu, and it has come to mean have its current meanings.