From the writings of St. Mary Margaret Alacoque:
"What a weakness it is to love Jesus Christ only when He caresses us, and to be cold immediately once He afflicts us. This is not true love. Those who love thus, love themselves too much to love God with all their heart."
"Let every knee bend before Thee, O greatness of my God, so supremely humbled in the Sacred Host. May every heart love Thee, every spirit adore Thee and every will be subject to Thee!"
"One cannot love without suffering. He [Jesus] showed us this very clearly upon the cross, where He was consumed for love of us. And it is still the same every day in the Blessed Sacrament of the Altar... Since love makes lovers one in likeness, if we love, let us model our lives on His."
"Love keeps Him there [in the Blessed Sacrament] as a victim completely and perpetually delivered over to sacrifice for the glory of the Father and for our salvation. Unite yourself with Him, then, in all that you do. Refer everything to His glory. Set up your abode in this loving Heart of Jesus and you will there find lasting peace and the strength both to bring to fruition all the good desires He inspires in you, and to avoid every deliberate fault. Place in this Heart all your sufferings and difficulties. Everything that comes from the Sacred Heart is sweet. He changes everything into love."
"In order to be like You, who are always alone in the Blessed Sacrament, I shall love solitude and try to converse with You as much as possible. Grant that my mind may not seek to know anything but You, that my heart may have no longings or desires but to love You. When I am obliged to take some comfort, I shall take care to see that it be pleasing to Your Heart. In my conversations, O divine Word, I shall consecrate all my words to You so that You will not permit me to pronounce a single one which is not for Your glory.... When I am thirsty, I shall endure it in honor of the thirst You endured for the salvation of souls.... If by chance, I commit some fault, I shall humble myself, and then take the opposite virtue from Your Heart, offering it to the eternal Father in expiation for my failure. All this I intend to do, O Eucharistic Jesus, to unite myself to You in every action of the day."
Source for the quotes and more information on devotion to the Sacred Heart of Jesus can be found here.