As part of its excellent series on careers in financial services, the Guardian has spoken to the girlfriend of someone who has recently become an a junior banker in M&A.

Needless to say, their life together has changed substantially. She seems more perplexed than annoyed, but her insights are accurate. If you’re thinking of working in M&A, this is what you need to know.

1. You have to really want it

“He always wanted this, to go into banking,” says the girlfriend. “I remember how one time back in our college days, we talked priorities. For me, it was happiness and being surrounded by loving people. For him, that came second. The job was first.”

“He is incredibly competitive,” she adds. “He’s got more willpower than I’ll ever have…”

2. It will take over your life

When he was an intern, her boyfriend’s hours were 9 a.m. to 7 p.m., says the girlfriend, but, “In the first week when his proper job started, it was work 'til midnight every day. It’s crazy how you adapt to that. These days, when he finishes at 10 p.m., I think to myself: ‘Wow, that’s really good.' When he comes home really late, he’s had six Red Bulls and he’ll want to talk. But I’m exhausted. I am thinking, tomorrow morning we’ll have a chat and sleep in. But then he gets an e-mail, saying: ‘Be in the office tomorrow by 9 a.m.'"

And when you do escape? “A little while ago, we were having dinner and he got a message that he had made a mistake. This threw him off completely. He couldn’t stop fidgeting, wouldn’t listen to me. The rest of the evening he’d fret about work. Everything has become provisional. When we plan something, he says, ‘But I may have to cancel.’ When we’re out, there is always the chance of him getting called back into the office.”

3. You will get fat and feel pressured to drink

“I tease him about his weight gain,” says the girlfriend. He doesn’t drink, but: “This is not making things easier for him at the bank. In fact, his parents have said that if he has to drink to get ahead at the bank, then this is okay.”

4. You will be financially empowered

“I live with my parents. I have huge student debts, a big overdraft … Now he has a really good salary, he looks smart – suddenly he holds all the cards in the relationship. He says things like, let me take you shopping,” says the girlfriend.

5. You will work with alphas

“These colleagues of his, they are like super people. Incredibly good-looking and intelligent and accomplished,” the girlfriend observes.

6. But those alphas will have no perspective

“Sadly, all they can talk about is work. Same with his roommate who is with the same bank, but in a different division. You will not believe how boring and childish conversations between the two can be. Who works harder, how to get into the right jobs, how hard it is – they can go on all night. ‘My bank is better at M&A.’ ‘But my bank is great at…‘“

7. The work you do will actually be mundane and boring

“He’ll be telling me that he spends at least half his time formatting documents, measuring the space between lines to make sure everything looks perfect. Presentation is so important in banking.”

8. People around you will crack

“He has this colleague who cries all the time. She can’t take the pressure… She’ll be crying in the toilet and he’ll cover for her, make up excuses why she isn’t at her desk.”

9. You will want to get out – after a few years

“I asked him if this job is want he wants to do with the rest of his life and he answered no. I was so surprised… He told me he wasn’t completely sure [how he saw his future] but that he would have to slog it out as an analyst for a few years. After that, he could practically go into anything.”