Why is Marriage So Difficult

Why is marriage so difficult? Why do two people who love each other or once loved each other, end up hurting each other?
The Bible is honest when it says, Marriage is Suffering, but it also speaks about how marriage is ordained by God. God created man and woman and told them to be fruitful and multiply. He also said that when a man and a woman marry two will become one.
So why is there suffering in marriage, the answer is simple. We are all sinners. You might be a good person but that doesn't stop you from being a sinner. We are selfish and full of pride and even when we do good things, there is always a self-interest behind it.
Two will become one. Two people with different backgrounds, different experiences and different temperaments are slowly becoming one, and this is a painful process.
So how can we persevere through the pains and sufferings. Here are a couple of suggestions, one is to include God in our marriage and the other is to change our way of thinking concerning marriage and suffering.
Our pride and selfishness leads us to believe that marriage is only about us, and that our spouse should be there to satisfy all our desires. So when they don't do that, we react by trying to make them feel as bad as they made us feel or by looking for a way out of the relationship, either with divorce or looking for somebody else who you think will really make you happy.
If we involve God in our marriage, this doesn't mean that you will never suffer, you will suffer because like I said earlier, you married a sinner. If we involve God in our marriage then we know God wishes for us to be like Him. And one of the tools that God uses to mold us and change us is other people, including your spouse or should I say especially your spouse. Since it's the person you spend the most of your time with and knows intimate things about you that others don't. So when we suffer in our marriage we should ask ourselves, what does God want me to learn from my spouse and this experience.
What does God want to change in Me! Now that's different since most of the time we're thinking about how the other person should change.
But the amazing thing is that if both spouses have the mentality of, "what does God want to change in me", then you will grow as a person and you will seek to change for the good in order to be a blessing to your spouse which in turn will bless your marriage.
If only one spouse has this mentality, then it will be a little more difficult, but there is still the chance that maybe through your example and Godly love, your spouse will change.