I've heard some good excuses, but THAT one...
Let's talk about what Jesus meant when he was referring to cutting off a hand or taking out an eye. These are things which were very well understood at the time but which are missed a lot today, I think.
If you look at the way the Jews of that time discussed things, you will see time and again in the parables, in the discussions -- all the way through -- that spiritual things are often discussed in physical terms. When Nicodemus asked Jesus "can a person enter again into the mother's womb" regarding being born again, both Nicodemus and Jesus knew that this was not the real point and so that was never discussed. But it was the physical picture Nicodemus understood about the 'born again' problem -- can one start all over again? And Jesus approached that.
This discussion by Jesus in Matthew 18 goes along the same lines. In Hebrew culture, the hand was the symbol of strength of a person. The right hand was the greatest strength, and thus Jesus is sitting at the 'right hand' of God. The foot was the action of a man, what he did and where he went. The eye was the understanding of a man.
We have very similar usages in English today. "Don't go there..." in a conversation is not a warning about you actually 'going' someplace, but an idiom for dealing with a certain subject. "Give me a hand, will you?" is another idiomatic phrase indicating the person needs your help, your strength. And the very common expression, "Do you see?" is exactly the same in the Hebrew culture -- "Do you understand?"
So what Jesus was saying in terms of these idioms is that if some area of strength in your life is causing you to sin, get rid of it -- abandon it. If your talent is music, and yet you find yourself drawn over and over again to the kind of music which is not honoring God, forget that talent -- at least for now. God is more important.
If you are doing something in your work or normal life which is getting in the way of your relationship with God, get rid of it. Withdraw from it.
And if you think you 'understand' something, but that something is denying the Biblical truth, get rid of that 'understanding'!
Note that Jesus said 'if' one of these things causes you to sin. You can be talented, doing many things, and intellectually gifted and none of these things might be getting in the way. They may have all been given into Christ's total control. That is wonderful.
But, for most of us, some of the things we are most proud of and most skilled at really do get in the way. Then which do we choose? Jesus said it is better to enter life without one of these things than to be condemned to hell.
The other way of looking at this is from the more 'negative' side. How on earth can a hand, or a foot, or an eye 'cause' you to sin? They can't. They are under the control of your mind and heart. So it is the expressions of the mind and heart Jesus must be referring to here.
And, as every other person has stated, this is not a commentary on marriage.
But, as one last thought -- and asking for comments from my Christian brothers and sisters -- suppose a husband was literally causing a wife to sin? Suppose a wife was causing a husband to sin? This could be in terms of cheating on income tax forms and both having to sign it, or something like that.
What then?