I work using my 2nd language, here's what helps for me:
1. I set up my phone to be on this language, I also try to consume as much as content possible in said language, so anytime you watch something on NF or YT try seeing if the same content is available in the 2nd language you'll use at work
2. I never, ever, plan or brainstorm anything using my native tongue, even outside of work. If I need to design or plan something I make sure to do it entirely in my 2nd language -- basically the gist is to get your brain used to _think_ in this language, the less you translate the more likely you'll be successful imo. Of course there's exceptions to this rule, are you writing a shopping list that needs to be shared with a family member? If so there's no point in doing that in a language they won't understand
3. Following up on #2, never translate words. If you stumble upon a word you haven't seen before try looking up its meaning using a dictionary in the 2nd language you're practicing instead of using google translate. You want to build the habit of understanding new concepts/meanings in your 2nd tongue as much as possible, because this is what will happen on your day-to-day at work, no one will translate alien/new concepts for you at work
4. I used to record myself and compare my pronunciation against native speakers reading the same content I just read, I don't do this anymore but it helped a lot in the past. You can use free books like the ones from the Gutenberg project for this, there's plenty of people narrating them on YT
5. If you don't have friends/people to practice your 2nd language try looking for a Discord server with voice channels in said tongue. I'm a book-case definition of an introvert/asocial person, but if I had not pushed myself to speak with strangers during my learning period I don't think I'd be successful in working with my 2nd language today.
6. Relax! My coworkers know that I'm not a native speaker, and when I'm struggling with something they often slow down their pace or try using simpler words/terms. Humans can be an ass sometimes, but ime in most occasions people will take the opportunity to help others when they can (esp. if there's nothing for them to lose). As I write this I recognize that I spend a good amount of my time volunteering and doing charity, maybe we are hard-wired in the brain to contribute back to others/society in any way we can?
> Anyone lived through this? How?
I think the "How?" can be answered by my tips above, as for some anecdotes once you get past your first few months of working in a 2nd language most of the stress/anxiety wanes down, if you're planning for accepting an opportunity where you'd have to speak another language I'd recommend you trying to talk to strangers as much as possible first.
The reasoning behind that advice is simple: if you can't hold conversations when there's nothing at stake then you need to practice more. Once you're in high stake situations you'll feel a slight hit to your speaking skills, it might be better to practice as much as possible first in a relaxed environment to see if you could handle having deep conversations in another tongue.
Unfortunately, the advice to talk to strangers is one of these things that are easier said than done, you'll need to build the skills to understand when a pen-pal or conversation is going to be productive or not. You want to prioritize having conversations with people who can stimulate growth in your 2nd tongue, e.g are their answers too short, or just basic yes/no? do they ask questions back to you? in your conversation are you exploring new topic/ideas? etc.
If you don't feel confident that a conversation is helping you with your long term goals then I'd advise stopping it and try looking for someone else to train with. The goal is not to make friends in this process but to create an environment where you can reserve about 1~2 hours of your day to extensively practice your 2nd tongue. For example the first time I played a TTRPG was over discord with random strangers in my 2nd tongue, I never played anything of the like before and it was an interesting experience to learn both the game and to have myself navigate in so many random scenarios using another language