All the descriptions of the 3rd functions are harsh. That's because the 3rd function is similar to the socionics polr.
The 1rst function is an area that you master very well but that you don't compromise with. You also don't need external validation when it comes to it. I knew I was 1W because I'm always aware of what I want and I am not easily influence by the will of other people (I'm aware of it but I don't really care because I don't compromise when it comes to my will and I don't expect other people to compromise when it comes to theirs).
That's why 1W conflict with 3W. 3Ws have a lot of insecurities regarding their own willpower. In a way they are strong-willed but at the same time they doubt themselves a lot. They want a lot of things but they don't really know what ("Oh I want this! But wait... Maybe I don't. What should I do?). They need someone to reassure them, someone who will take the time to discuss their desires and ambitions with them. It's through this exchange that they gain confidence. A funny representation of 3W is Chidi from The Good Place, even though it's obviously exaggerated for the sake of comedy:
The 2nd function is different from the 1rst one because even though you are really good at it, you are more than willing to compromise; actually you even need external validation in this area (it's a processing function). So for example I'm 2E and I'm very aware of my emotions but I love to talk about them and over-analyze with my friends, I could do that forever. Having this interaction helps me to understand my own emotions even better which is important for me because I aspire to mastering them completely. I also enjoy helping people who struggle with their own emotions and I'm pretty good at it. I find people who are genuine and insecure emotionally particularly endearing.
On the contrary, someone who is 1E wouldn't understand my need to analyze my own emotions like that, for them emotions are just emotions, you just feel them or you don't and they might think that I overcomplicate everything.
1rst function = you consider that you are already perfect, no need for external help/validation
2nd function = you are a perfectionist, you want to help people perfect themselves and reassure them all while working on yourself by doing that.
3rd function = you are insecure, you might even feel shame and you constantly need to learn and to be reassured
4th function = you just don't care
1rst and 4th functions = terminal = I am what I am, I feel what I feel, I think what I think. Who cares? Don't bother me please.
2nd function and 3rd function = processing = we can always improve, let's talk about it, let's work on it together. I'll teach you. Please teach me.
Keep in mind that I'm 1W so my view of 3W is likely to be biased.
Edit: Also 3W people are the kind to fear being taken advantage of a lot. They can be scared that other people will try to impose their own willpower on them so you need to be careful and reassure them that you don't have ill intentions when you deal with them.