I will jump quickly to what Paul says on the matter:
To the unmarried and the widows I say that it is good for them to remain single as I am. (1 Corinthians 7:8, ESV)
What Miyamoto Musashi is talking about here is strictly from the point of view of having a completely devoted life to pursuing "The Way". As a Christian samurai "The Way" is not the pursuit of Bushido, but the pursuit of our Lord Jesus Christ. I can speak from personal experience on this one. I have been married to a wonderful woman for over seventeen years, and i am very grateful to God for her in my life. God uses this woman, and our children, in my life to help me grow. However, my focus is not continually upon the Lord now that i am married. I need to make sure that i am providing for her and our children. The cares of the world creep up much more frequently because i cannot just dismiss this or that concern. But, when one is single, it is much easier to focus solely on God. You can think less of yourself and be more readily available. Sort of like when Jesus sent out the seventy two. (Luke 10) He instructed them, "Carry no moneybag, no knapsack, no sandals, and greet no one on the road." (Luke 10:4, ESV) Ever try and travel with a baby? You practically double your load. Now having said all this, not everyone is called to be single.
But if they cannot exercise self-control, they should marry. For it is better to marry than to burn with passion. (1 Corinthians 7:9, ESV)
Being married does not eliminate you from being able to serve the Lord, but you need to understand that it is a restraint and your focus of learning and conforming is different than that of an unmarried/uninhibited follower of Christ. If you are married, stay married, but if you are not... consider remaining single. The whole chapter of is an excellent illustration of God's instructions to us in this regard.