Something Muslims do that Christians Should, Say "If the Lord wills"

Muslims probably borrowed a number of practices from Christians that are actually Biblically. Many Muslims will say, "Inshallah' before making plans, which means "If God wills.'

James 4 teaches Christians to say 'If the Lord wills' while stating their plans for the future:

13 Come now, you who say, “Today or tomorrow we will go to such and such a city, spend a year there, buy and sell, and make a profit”; 14 whereas you do not know what will happen tomorrow. For what is your life? It is even a vapor that appears for a little time and then vanishes away. 15 Instead you ought to say, “If the Lord wills, we shall live and do this or that.” 16 But now you boast in your arrogance. All such boasting is evil.
(NKJV)

Since you do not have power to keep yourself alive, when you state what you will do in the future, you should acknowledge that it is dependent on God. i have had even fellow believers think ill of me, as if I did not want to commit to them, for saying this. But the Bible teaches it.

In I Corinthians 4:19, Paul says "if the Lord wills' while stating his plans.
But I will come to you shortly, if the Lord wills, and I will know, not the word of those who are puffed up, but the power.
(NKJV)

He makes a similar statement in I Corinthians 16:17
7 For I do not wish to see you now on the way; but I hope to stay a while with you, if the Lord permits.

And when the author of Hebrews got to chapter 6, he would continue teaching on certain subjects 'if the Lord permits':
Hebrew 6
6 Therefore, leaving the discussion of the elementary principles of Christ, let us go on to perfection, not laying again the foundation of repentance from dead works and of faith toward God, 2 of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment. 3 And this we will do if God permits.

I concur with your estimation and a Christian should not take anything for granted.

I think most of the time, Not the
"If the Lord wills"
but "If I think if the lord wills"
then became "if I will"
Muslims are a good example. The Koran says that if you shed innocent blood, Allah will not hold you innocent

I think many Christians have the same problem

This has always been a practice in my family. Everything depends upon the will of God. I believe most who believe have this asttitude in their walk with Jesus Yeshua, , and most do say the same.