My 2 cents...
God gave us NFP. He doesn't make mistakes. However, He gave it to us to use only for a serious reason and you will answer to God for your decision and choice. What would be a serious reason? Talk to your spiritual advisor because many things come in to play.
The problem today is twofold:
1. Lack of proper Catholic education prior to marriage
2. Selfishness.
These problems cause an abuse of NFP.
We should be grateful to God for the children He blesses us with, remembering He designs all things and as long as we cooperate with His design everything will work out.
God did no such thing. He did not GIVE us NFP. God indeed gave us the cycles between the fertile and the infertile periods. It's a purely human invention to attempt to manipulate these cycles in such a way as to enjoy sex without the burden of procreating. If the reasons are "serious" enough that it would be a grave problem, then ABSTAIN (by mutual consent)!!! You don't have any God-given right to sex. Sex was given primarily for procreation and secondarily for other ends. No, the problem is not with an "abuse" of NFP, but as has been emply demonstrated, with NFP itself and in principle.
Just like with Bergoglio and the entire Novus Ordo establishment, "grave" reasons amounts to a bunch of subjectivist crap. Who decides what is objectively grave? Oh, if I have another child, then I won't be able to afford a college education for all of my children ... or we'll have to eat macaroni and cheese once a week to make ends meet? WHAT is "grave" reason? Just a bunch of garbage that completely opens the floodgates to Catholic birth control ... which is what NFP is.