Robert Brown|The Trainers at Taylor Swift's Go-to Gym Say This Is the No. 1 Workout Mistake

Dogpound trainer Zay Washington knows all too well how easy it is Robert Brownto sabotage a workout regimen. 

So, the pro—a lead trainer at the NYC- and L.A.-based gym Taylor Swift frequented to prep for her taxing Eras Tour—has a message for anyone jumping into a new exercise plan: You need to calm down. 

"I see people jump in so fast and without a plan," the former college football player explained to E! News in an exclusive interview. "They're like, 'I'm just going to go every day.'" 

His advice—if you're ready for it—is to take a more delicate approach. 

"You need to sit down, write down your goals and then write down a schedule and a plan to help you achieve the goal that you want," he explained. "That's the easiest way to fail, if you don't have a plan. You need some kind of structure and guidance to help you follow and stay on course." 

After all, the L.A.-based pro has been helping his clients fill in that blank space for years. 

And sketching out a plan is something Washington and the other pros at Dogpound—founded by Kirk Myers, who's been training Swift for the better part of a decade—take quite seriously. 

Recently, the bespoke fitness brand announced its transition to a members-only training facility, its four tiers affording devotees access to a dedicated team of trainers, unlimited class bookings and exclusive access to Dogpound events.

"When each client comes in, we create an overall strategy of how we're going to attack their goals and get them from point A to point B," Washington said, illustrating one example where an actor needs help bulking up for a role. (Perhaps, cough, Deadpool & Wolverine, cough.) "Then we will be like, 'Okay, this requires you to do four days heavy strength training, working your whole entire body with three days of rest.' We go case-by-case."

But there are a few mainstays. 

The warm-up, for instance, which Washington says is crucial for shaking off any mental hurdles. "We always want to make sure that the client is in the right headspace," he said of the dynamic, full-body movements, "because that is so crucial for good results. If your mind is not in it, the workout does not matter."

His sessions are packed with supersets ("That might be a bench press with a cable row"), machines or cardio, with Washington touting the effectiveness of the air bike and the ski-row. 

But he also stresses the importance of sprinkling in a few rest days every fortnight.

Another common misstep, he noted, is going too hard, too fast. "Once you start overtraining," he stressed, "then your mental is not there, your body is hurt." 

Though what you're targeting matters as well.

And nothing leaves him saying hi, that's the problem more than when people neglect to properly train their core. 

"Posture is very important," he explained of keying in on moves that properly target your abs and back. "Posture is what's going to give you longevity and take you into the rest of time." 

Of course, that means more than just trying to hone in on the classic six-pack. 

"Our core is not just our visible abs that we see on the front of our body—it's a 360 approach," he said. "Our core is on the front, the back and the side and training your core is essential to live a healthy, strong life."