All the lord Vishnu followers have an important day to relish the fasting as today happens to be Yogini Ekadashi. The day falls on in the month of Ashadha during the Krishna Paksha—the waning phase of the moon, as per Hindu calendar. Therefore, this year it is observed on June 30.
The devotees usually keep a fast on this day as this Ekadashi is said to be important for all those who seek to get rid of all their past sins, assuring good health as well.
King Kuber was a staunch Shiva devotee, and would worship the lord daily by offering flowers to the lord. There was a gardener named Hem Mali, who was a Yaksha. He would get Kuber flowers on a regular basis from the Mansarovar. However, once he did get the flowers but forgot to give it to Kuber as he was busy spending time with his beautiful wife. As a result, the king sent his servant to find out the real reason behind Hem's negligence.
After he got to know about it, Kubera got extremely angry and cursed Hem to suffer from the deadly disease of leprosy and ordered him to stay separated from his wife. Hem was out of the palace and suffered immensely due to the disease. After wandering for many years in the forest, Hem came across the ashram of Rishi Markandeya, who after listening to his story advised him to observe Yogini Ekadashi Vrat.
Hem Mali kept the fast with full devotion and prayed to lord Vishnu of forgiveness. As a result, Lord accepted his prayers and Hem was cured of all his sins. He was free from any disease and reunited with his beloved wife once again.
Similarly, all the devotees observing this fast and praying to lord Vishnu with pure thoughts and feelings shall be freed from all their difficulties and health related issues on Yogini Ekadashi.
You can pray to the lotus feet lord by chanting Vishnu mantras or Vishnu Sahasranamam.