What mystery lies behind our failures in the tests that life holds for us? Well, none of that, the answer will be found within us. 

“Therefore, since we are surrounded by such a great cloud of witnesses, let us throw off everything that hinders and the sin that so easily entangles. And let us run with perseverance the race marked out for us.” Hebrews 12:1

Because your faith is not strong enough. Many times I have heard that prayers do not work or that God does not have time to listen to this or that person. Perhaps the answer is in our Faith that is why we must analyze and verify what state it is before facing a test. In this case, it is best to exercise it conscientiously so as not to make the same mistakes.

“Rejoice greatly, Daughter Zion! Shout, Daughter Jerusalem! See, your king comes to you, righteous and victorious, lowly and riding on a donkey, on a colt, the foal of a donkey.” Zechariah 9:9

Because the tests you pass still don't allow you to grow. Let us remember that the obstacles that God puts in our path towards Him not only test our Faith, but, if overcome, they also grant us virtues that we did not have until that moment, and everything contributes to making us grow as individuals, but Perhaps what happens is that we need to repeat the test again and again until we achieve the goal that God intends in the way He wants.

“Fight the good fight of Faith; make your eternal life, to which you were called and for which you made that admirable statement of Faith in front of many witnesses.” Timothy 6:12

Because God does not want it. But it is important to keep in mind that this is not a divine whim, far from it, it is only that God is the only one who knows your potential and how much you can give if you set your mind to it, and since we know that Christ does not go with half measures, He wants you to give everything, just as He did when He gave His life for all of us.