I don't think I've ever heard any Christian saying that marriage is easier because its Christians involved. Marriage is hard. People are sinful, and we screw things up. Left to our own devices and refusing to allow God to be the glue of the marriage... i'll just say its no wonder so many Christians seek divorce if they don't include God in their marriages.
But life is hard. Especially from a Christian perspective. We're literally guaranteed that life will be hard, regardless of marriage, throughout Scripture because we're Christians. Does that mean we should do away with faith? nope. Because Christians have something that nonChristians don't that gives us hope and strength. In all situations.
11 Not that I speak in regard to need, for I have learned in whatever state I am, to be content: 12 I know how to be abased, and I know how to abound. Everywhere and in all things I have learned both to be full and to be hungry, both to abound and to suffer need. 13 I can do all things through Christ[
b] who strengthens me. - Phil 4
2 Consider it pure joy, my brothers and sisters,[
a] whenever you face trials of many kinds, 3 because you know that the testing of your faith produces perseverance. 4 Let perseverance finish its work so that you may be mature and complete, not lacking anything. 5 If any of you lacks wisdom, you should ask God, who gives generously to all without finding fault, and it will be given to you. 6 But when you ask, you must believe and not doubt, because the one who doubts is like a wave of the sea, blown and tossed by the wind. 7 That person should not expect to receive anything from the Lord. 8 Such a person is double-minded and unstable in all they do. - James 1
6 Humble yourselves, therefore, under God’s mighty hand, that he may lift you up in due time. 7 Cast all your anxiety on him because he cares for you. - 1 Peter 5
I think thats something important to realize long before marriage ever enters the picture. If we, as singles, do not know how to rely on God to be our strength when we're weak and going through trials, we won't know how to do that in our future marriages.