“He that hath received his testimony hath set to his seal that God is true.”  
John 3:33

A seal is used by brands to validate a product as their own creation. When you see a phone with an “eaten apple” logo/ seal, you expect to use that phone as an iPhone and it’s features would be different from the features of any other phone with an android OS.
With the seal, you know what to expect from the phone and with the seal, you know what accessories would work with the phone, you can’t use a USB type C cable on an iPhone, the seal signifies to the world, what should be given to the iPhone.
Bringing it home, he says the man who receives God’s testimony has set to his seal that God is true; he has communicated to the world that in his life God is true, maybe there are economic hardships and everyone is receiving a lesser portion than what they’re used to, everyone except the man who has set to his seal that God is true- “all things are working together for his good”- and that is his expectation, that is the accessory he’d be given, a demotion for everybody but a promotion for him.
There’s a pandemic? Not for the man whose logo states God is true, he’d always “put to death the transactions of the body.”