Watch the video of OBW to break your patterns of unhealthy breathing.
With the box breath you greatly risk creating tension in the gut which of course Seals or cage fighters and other combatants have no problem with as their belly is hard as a rock/washboard, but that simply adds to the tendency to not be able to relax and let go in the belly area (even after the contest or war is over) which is where deepest relaxation resides and the absence of which invites a host of health and emotional/energetic challenges/disasters. Prescription drugs will not cure this as they only address reducing the over stimulation part, not the deeper easier relaxing breathing part.
Majority of seals get divorces because they are very hard to live with. Relaxation is not an option in combat. Calming may be an option, but that is not deep relaxation. They are VERY different.
“The Navy has the highest divorce rate of all the services. Among the Navy, the SEALs have the highest divorce rate. Read: Why is the divorce rate among US Navy Seals over 90 percent? - Quora
Good people but the stress takes it toll.. What is needed is rock-solid grounded parasympathetic based breathing that allows the body to rest, digest and heal. Otherwise the breathing pattern stays in partial or complete fight or flight. OK, if you are a SEAL then survival is a very big deal.
Another reason why I integrate in my optimal breathing kit the voice strengthening as that can also weaken or strengthen the breathing foundation. For example, if you are an opera or classical voice singer, you need to relax your belly and, counter intuitively, as you get better at that your voice gets stronger.
The key is to slow down the exhale #3 so you get up to a higher count (I at age 78 can do 40 or more) and still have a passive exhale left at the end. Leak it out.
Then let the breathing decide when to inhale and repeat 10-20 times adding a number each rep, but never add a number unless you have successfully achieved/allowed the passive exhale. Stay with that number until you have achieved the passive exhale.
Can't emphasize this enough. Make sure you always have some passive exhale at the end of #3 where TENSION resides.
Start at 4 in, skip the hold as it helps create restrictive chest tensions, and 4 out, and build up slowly one number at a time and never try to exceed an exhale # that did not have a passive exhale left.
You may already be pretty relaxed, or at least think you are, but just see how you do.
The higher the number you achieve, the more relaxed you can be and the more it will stick/sustain.
Make 40 your ultimate goal.
That might take days to weeks.