When you're trying to say that you will be mindful of how you say things in the future, you can say:
-I will be watchful of what I say.
-I will watch my words from now on.
-I will be more careful about what I say.
This will indicate to the person that you will be careful of what you say in the future.
[これから](https://eikaiwa.dmm.com/uknow/questions/7573/)は[発言](https://eikaiwa.dmm.com/uknow/questions/57282/)に気をつけると伝える言い方です：
-I will be watchful of what I say.
言うことに気をつけます。
-I will watch my words from now on.
これから言葉に気をつけます。
-I will be more careful about what I say.
言うことにもっと気をつけます。
これから先は発言に気をつけると伝えています。
I’ll be more careful about what I say. 「[発言](https://eikaiwa.dmm.com/uknow/questions/57282/)により[気をつけます](https://eikaiwa.dmm.com/uknow/questions/42478/)。」
このように表現してみてはいかがでしょうか。ご参考になれば幸いです。
I will be more careful about what I say in the future.
"I will think before I speak next time.": To think before you speak means that you will give more thought to what you say before you say it.
"I will be more careful about what I say in the future.":To say that you will be more careful means that you won't say something meaningless.
"I will think before I speak next time."
次は、考えて話します。
To think before you speak とは、言葉にする前によく考えて発言するという意味です。
"I will be more careful about what I say in the future."
今度は、言葉にもっと気をつけます。
To say that you will be more careful とは、意味のないこと、失礼なことを言わないという意味です。
If you are wanting to tell someone you will watch what you say then you could use 'watch what i say', 'watch what i'm saying'.
To be careful also means to watch and take care not to upset anyone.
発言に気をつけると伝えたいなら、「watch what I say」、「watch what I'm saying」
が使えます。
「be careful」も、怒らせないように気をつけることを表します。
To mind your words means to think about your words or use your 'mind' before speaking.
Holding your tongue means not to say something; especially if you have not thought about it carefully as it may cause offence.
「To mind one's words」は「言葉に気をつける、考えてから話す」という意味です。
「Holding one's tongue」は「〔人の気分を害さないよう〕言わないでおく」という意味です。
Here you are being quite self-critical as you must have said something which has caused a bad or unexpected or dramatic reaction. It seems you have not been attuned to the circumstances, or sufficiently sensitive when speaking.
The two sentences you see provided above are terrific ways to express to your listener that you want to be more careful about what you say. In the first sentence you will notice the term watch oneself. This means to be very careful about what we say or do. In the second sentence you will notice the phrase watch one's tongue. This means to be careful about what we say. Both of these terms are common in our everyday conversation and they would make great additions to your vocabulary.
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