In the Second Reading, Paul says that if Christ is not raised, your faith is in vain. This is a hard saying. Faith is meant to make a person fruitful, like a tree planted by running water, as the Psalm says. Why would a person not be fruitful if he thought there was no resurrection?
Well, the fruits of a life are the fruits of the indwelling Holy Spirit. Here are the first four: love, joy, peace, and patience. If God is indwelling within you, then he is present in love to you; and love, joy, and peace come from the presence of your Lord. It is easier to wait in patience through the afflictions of this life if God is with you, too.
And here we should notice that you can lose the fruits of the Spirit and become a fruitless person whose faith is in vain in different ways.
The First Reading says that you will be like a dried up plant if you put your trust in the things of this world. You can lose your job or your health or your spouse, for example. And then if you trusted in the things of this world, you would become bitter because your career or your life or your relationships would have failed to be what you trusted they would be. You wouldn’t be fruitful in love, joy, and peace in that condition.
But you can go wrong another way too. In the Gospel Reading, Jesus says that those who are hungry and weeping and hated are blessed. If you think there is no resurrection, you will think that being in so miserable a condition is the best you will ever have. And then you will certainly lack love, joy, peace, and patience. Then you will be both bitter and self-congratulatory in the mistaken view that you are spiritually advanced because you take denying yourself as a good in itself.
So for your faith to be fruitful, you do need to believe that there is a life after this one where there is no more hunger, weeping, or hatred. If you grasp that after the crucifixion of this life, there is the life of the resurrection when God himself will wipe all tears away, then and only then will you be fruitful in love, joy, peace, and patience.