Pre-approval???

I decided to go ahead and apply for the loan.  The first company turned us down.  I tried another company and they called me tonight to let me know they have pre-approved us for the full amount we are asking for.  I still can't believe it.  I'm getting the rest of the paperwork together tonight. I have this fear it will be taken away from us in an instant.  I guess I've been dealing with rejection and let downs for so long it seems unreal that we have this.  I guess I'll feel more secure once we get the loan.  I finally feel like I can start planning for our cycle.