I think he's referring to the fact that after 10 years people change, sometimes not always in the same direction as one another and thus parting ways is the more intelligent decision rather than live in misery or deny your personal growth for the sake of a relationship, and your obvious lack of knowledge of this basic fact of life as it pertains to relationships and people in general shows an amazing lack of life experience on your part.
Personal growth is pre-determined based on individual personality factors. This growth is just drawing conclusions from events that occur around you and applying it to your own personal knowledge factor. People don't spontaneously go from ying to yang without a cause.
Meaning, people are logical beings, even if their logic is faulty, they still try to make the decisions that they perceive as best for them. Thus, it should be simple enough to predict what will happen to a person who shares (more or less) the same future life experiences as you, assuming you know their past life experiences and how they reacted to them (if you are marrying someone and having a child with him/her, you damn better know about his/her past). People aren't random, our actions are not random neuron misfirings. We still retain free will, and exercise it as we see most helpful to our goals.
If you fail to properly predict how someone will change when they share a life with you, you have failed to properly analyze their personality. In such a case, you should have never married/impregnated her in the first place.
But damn bro, no need to conjure up excuses, nowadays a large number of [irresponsible] teens get pregnant/married on a whim.
It's understandable, marriage generally occurs as a hope of preventing yourself from ending up a pathetic loner (seeking someone to help you out during the rough times, because you are not independent enough to survive on your own). Then children generally occur in hopes of keeping a failed relationship together. The world is populated with irresponsible people, you're one of them, no matter how much you make up for your past mistakes, you can never erase what you have done.