Saying "no" to a boss can feel impossible.

Whatever our job, we all want to impress rather than disappoint.

But ambition can be a very slippery slope. Before you know it, work is coming home with you - seeping into weekends and disrupting time with family and friends.

Experts agree that learning to set boundaries is the way to stem the flow.

Career coach Helen Tupper, co-founder of Squiggly Careers, suggests a simple language shift can help reinforce boundaries.

She recommends replacing "I can't" with "I don't".

"I can't" invites negotiation - people might try to convince you that you actually can," she says.

But "I don't" is more definitive and harder to challenge.

For example you can say "I don't go to meetings after 5pm on a Wednesday because I pick my kids up then," she suggests.

Model and TV chef Lorraine Pascale says not doing this ultimately led to her burning out.

Alongside her television career, she opened a patisserie in Covent Garden and published a series of cookbooks, all whilst raising her daughter.

"I just wasn't very good at saying no.

"You don't want to upset people, everyone's feeding stuff in your ear as to what you should be doing. So you just keep going," she told BBC Woman's Hour.

She adds that her perfectionism, including personally approving every recipe in her books, didn't help.

For Lorraine, burnout manifested physically and mentally - including "not wanting to go near" cakes.

"It was like an all-body reaction - a tightness in my chest," she explains. "I was having arguments with myself. A lot of self-blame, a lot of guilt, and a lot of tiredness."

Lorraine's experience shows burnout can affect anyone at any level, even if statistics suggest it is more likely to happen to women - in part because of added family responsibilities.

Dr Claire Ashley, author of The Burnout Doctor, says on a practical front, sticking to a firm routine over when you finish work each day allows our brains to complete the "stress cycle" and enjoy time off.

But the real solution is adjusting your goals to your "current capacity".

"Ask yourself whether what you want to achieve is reasonable given your mental and emotional resources at the time," she says.

In Lorraine's case this involved stepping back from cooking and going to therapy. This helped her understand that the toxic elements of her drive to impress stemmed from her childhood in foster care.

She's since begun studying psychology herself and says she is "much better" - gradually getting back into cooking on more "intentional" terms.

Of course, stress and long hours are part of any job.

But stats show an increase in the number of workers reaching breaking point.

Nine out of 10 workers have experienced high or extreme levels of pressure or stress in the past year, research suggests.

Feeling stressed or burnt out isn't the same as having clinical burnout - even if we often use the term loosely.

Dr Ashley says exhaustion, detachment, and reduced performance are the three defining symptoms.

Unless we meet all these, we don't yet have diagnosable burnout. But of course this doesn't mean we're not on the way.

'Run your own race'

Tupper, who wrote her book after experiencing burnout herself, says it's important to stop, celebrate and acknowledge your own successes, not just focus on the next thing.

Doing our best to avoid comparisons with colleagues can also help, so we run our own race, Tupper adds.

Of course, not everyone is in a position to push back at work - especially in corporate, or hierarchical job environments.

Dr Richard Duggins, an NHS psychiatrist and the author of Burnout-Free Working, often helps patients who feel they can't assert boundaries.

He encourages workers to talk to their boss regardless of how junior they are.

"Most employers, even the hard-nosed ones, will listen and make adjustments when they understand that preventing burnout benefits everyone."

He says setting boundaries, asking for help, or adjusting workload or flexibility can all help, but in the end if the workplace environment doesn't change then we need to make changes to protect ourselves.

Appreciating our life stages can be help with this, notes Dr Ashley.

"It's okay to say that someone working part-time, or with family responsibilities, may not be able to match the workload of a younger colleague."

As Lorraine puts it: "Ambitious is fine. Being ambitious is a beautiful thing, but just learn to say no more often."