How did you balance your own life plans with becoming such an involved and active grandparent unexpectedly?

Why might some couples survive tough times and grow stronger, while others may not, and what can be done to improve the odds of success?
Why do narcissists struggle so much with learning from their mistakes, and how can you effectively communicate criticism to someone who thinks they know everything?
What are some practical steps for maintaining a strong marriage when you're both emotionally and physically drained?