Expressing "always/continuously" with 总是 and 一直

In Mando we have two primary ways of expressing "always".  These two have pretty clear and different use cases once we understand the logic behind them.  These words are 总是zǒngshì and 一直yīzhí。

总是zǒngshì

We will start with 总是zǒngshì, since it is really close to the English word "always".  We will use it in situations like, "I am always so tired.",  "They are always hungry.",  "There is always traffic on I5", etc. 
总是zǒngshì expresses a general state and is a frequency word, like 常常chángcháng，经常jīngcháng. which implies something happens frequently.

These next few examples will make its use super super clear:

Zhèlǐ zǒng shì yǒu hěnduō rén. ——> There are always so many people here. 这里总是有很多人。

Wǒ nǚ péngyǒu zǒng shì hěn máng, hěn shǎo hé wǒ chūqù wán. ——> My girlfriend is always busy, (she) rarely goes out to hang out with me. 我女朋友总是很忙，很少和我出去玩。

Note that in each of these cases, we are making general statements about how the world always is.  This is pretty much how 总是zǒngshì works.  Note, none of these translate to "has always".  The English word "has always" is when we being stepping into  一直yīzhí's territory.

一直yīzhí

一直yīzhí serves a very similar purpose to 总是zǒngshì , but  一直yīzhí has some pretty different connotations.  The primary connotation is that  一直yīzhí will be used when there is an explicit or implied length of time.   For instance, if I am saying "from...until... it was always this way / has always been this way", we would use  一直yīzhí.  Really, whenever we would say "has always" or "was always", we will use  一直yīzhí and not 总是zǒngshì .

Wǒ jīntiān gōngzuò de shíhòu yīzhí juédé hěn lèi. ——> During work today，I felt so tired (the entire time.) 我今天工作的时候一直觉得很累。

Wǒ yīzhí xiǎng qù zhōngguó, dànshì yīzhí méiyǒu qián. ——> I've always wanted to go to China, but I've never had the money. 我一直想去中国，但是一直没有钱。

Tāmen cóng zuótiān wǎnshàng dào xiànzài yīzhí zài chànggē. ——> They have been singing from last night until now. 他们从昨天晚上到现在一直在唱歌。

Jīntiān xiàwǔ yīzhí zài xiàyǔ. ——> It has been/was raining nonstop this afternoon. 今天下午一直在下雨。

Important things to notice here are that each of these sentences has a "have been", "have always", "was always", or "nonstop", "continuously" kind of meaning in English.  This is the nature of 一直yīzhí.  

Let's look at a few more examples of them side by side to help clear out the differences:

✅	Xīyǎtú yīzhí xià yǔ. 西雅图一直下雨。	——> Implies some kind of time length.  I might think that before this there was a sentence like "over the last few years" or something that expresses the time.
✅	Xīyǎtú zǒngshì xià yǔ. 西雅图总是下雨。	——> "It always rains in Seattle".  Simple, no explanation needed.
✅	wǒ yīzhí xiǎng qù zhōngguó.  我一直想去中国。	——> "I've always wanted to go."; For several years now, you've had this desire.
❌	wǒ zǒngshì xiǎngqù zhōngguó. 我总是想去中国。	——> "I always want to go." If I ask you at any given minute on any given day, "do you want to go to Seattle", your response would be "yes. Let's go."  This feels weird and we would probably use 一直yīzhí
✅	wǒ yīzhí xǐhuān nǐ.  我一直喜欢你。	——> "I have always liked you." Simple, just like English.
❌	wǒ zǒngshì xǐhuān nǐ.  我总是喜欢你。	——> "I always like you."  Like the last example, this feels really weird.  What you are expressing here is that at every second on every day, you like me.  We will never hear 总是zǒngshì used like this.

Hopefully this makes enough sense for when to use 总是zǒngshì vs 一直yīzhí.  If you find yourself confused or unsure of when to use which, focus on 总是zǒngshì  for now, since it is closest to English's "Always" and we will help you gradually understand 一直yīzhí。