When you love in this way - when you are willing to be expiation for the failings, weaknesses, and faults of another - it's going to leave you empty. If you empty yourself for them, de facto, you have nothing left for yourself.
This is where our Lord promises us that if we do it for Him, for His sake, imitating His example, offering it back to Him in union with His cross, then He promises to fill us with His presence. That's what He means when He says "As I remain in You."
So it's conditional. Our Lord's love is conditional on the fact that He will remain in us, He will fill us with Himself if we fill those around us with the same offering.
When you're struggling in your life, when you realize "I feel like the Lord isn't really working. I feel like my relationship with the Lord is weak," ask the Him for an opportunity to sacrifice for somebody else. That may seem like the last thing you want to do because you're struggling. But that's the perfect thing to do. But that very sacrifice requires our Lord to then fulfill His end of the bargain. ...
You need to practice this in your family. When you find yourself struggling, especially with "that" sibling - every child who has brothers and sisters, usually there's that one at least that they struggle with the most - say a prayer. Ask the Blessed Mother, ask the Lord, "Give me an opportunity to show them some sacrifice of love." Spouses, you need to do this regularly with each other, especially when you're not getting along. Find an opportunity. Ask for one. And it will be given you.
You'll find in that moment when you sacrifice yourself, when you make a gift of yourself in whatever way, then the Lord steps in and fills you. With His presence. With His love. And everything becomes easy after that.
Audio homily is from the Vigil Mass with Father Miller. Video is from Sunday Mass with Father Sheridan substituting for Father. You may watch the Mass in its entirety on our YouTube channel. Fr Sheridan's homily begins at 15:30