It takes time to hit a groove in any new gig.

In fact, almost half of new hires – and a whopping 60% of managers – say that “learning the ropes” is the most challenging part of starting a job, according to one Accountemps survey. And that was double the amount of workers worried about getting to know a new boss or coworkers.

But how long do you have to learn the ropes? The “Today” show’s latest hire, Megyn Kelly, is already under fire for having low ratings – but she’s only been on the job for three weeks.

Plenty of hit shows took time to hit their stride, after all. “Seinfeld’s” 1989 series premiere counted only 15.4 million viewers. Its second season finale dropped to just 12.5 million. But the “show about nothing” became the unstoppable anchor of NBC’s “Must See TV” Thursdays by its fourth season, and the 1998 series finale net 76.3 million viewers.

And some of today’s top professional athletes had rough rookie seasons. Before becoming a Super Bowl MVP and breaking the NFL record for career touchdown passes, Peyton Manning’s first season with the Indianapolis Colts in 1998 saw him complete just over half of his passes. Indians pitcher Corey Kubler had a modest 2011 debut and a couple of middling seasons, but by 2014 he became the lowest-drafted player to win the Cy Young Award after pitching 18 wins.

Most of us don’t have years to prove ourselves, but three months should be ample time to acclimate.

“In a typical new job, 90 days is the sweet spot when it’s OK to fumble a little, make some mistakes, learn the ropes, pull in low sales figures/quotas, miss a deadline and catch a break,” Monster.com career expert Vicki Salemi told Moneyish.

See also: Hires’ Remorse: What to do if, like Donald Trump, your new job isn’t exactly what you thought it would be.

That’s with brand-new hires, she noted. Those transferring within the company should catch on sooner, because they already know the company culture and internal mechanisms – like getting a new laptop or learning your workplace’s acronyms – which would otherwise take awhile.

“There’s still a window when it’s OK to not be fully up to speed, especially when it’s a completely new role with a different skill set, but it’s typically less than 90 days,” Salemi said.

Unfortunately, there’s no legally-defined window when you are absolutely safe if your performance is not up to par.

“Employment here in the U.S. is ‘at-will’ unless your employer explicitly states otherwise, which means that you can be fired at any time for any reason (that isn’t illegal). You can be fired on your second day of work,” business law attorney and employment law guru Beth Robinson told Moneyish.

While many companies do include a “probationary period” to let your learn the ropes in their handbooks, Robinson warns that it is “a meaningless provision.”

“It doesn’t give an employee any legal rights unless employers expressly state it does, and I’ve never seen a situation where this provision has actually negated a termination,” she said.

So what are some signs that you’re in trouble?

You’re in way over your head. It’s healthy to overextend a bit and try new things – how else do you learn and grow? But if you really oversold your skills during the job interview, your boss is expecting big things up front. “For instance, if you work in sales and come from a competitor, and you already have an impressive book of business, then the ramp-up time from the start in your new job will be less, because expectations are higher for you to excel from the very start,” said Salemi.

You’re missing a lot of deadlines. “Missing a deadline or missing quota can be grounds for termination at any company on the spot … and a few months of missed quotas typically translates to a pink slip,” warned women’s empowerment and business expert Heather Monahan.

You’re hurting the team. Your low sales or low production numbers frequently create more work for your colleagues, or keep the entire crew from hitting a target. Executives and managers are also held to a higher standard because it’s their job to lead the team to success.

So what do you do if you suspect you’re in the red already? Address it head-on.

“You don’t want it to seem like you’re inadequate or subpar, but you also want to show the good news that you’re being proactive,” said Salemi. Broach the topic with your boss like this: “I’d like to sit with so-and-so on the team and shadow them for a few hours. They really have a knack for working with a few challenging clients. Do you have another suggestion on how I can quickly get up to speed in this realm?”

Don’t get defensive when your supervisor tells you ways to improve your performance. Take the advice with an open mind, and ask for specific examples on what to do, like, “What else should I focus on doing better?”

Tap your colleagues’ expertise. Besides possibly shadowing one, ask a couple how long it took them to get comfortable in the position, and what they know your manager is looking for in assignments. And if any teammates come to you offering help, don’t get embarrassed – accept it, and get ahead.

And demonstrate that you’re ready to make this work. Sign up for a tech refreshing course on using the operating system. Come in a bit earlier or leave a bit later to show you’re dedicated to taking care of business.

But whatever you do, don’t try ignoring it or hoping things just get better. Your boss can see when you’re struggling, and it looks bad if you don’t address it – or worse, if it appears you think that everything is fine, when it’s clearly not.