How does one become regular in prayer despite repeatedly abandoning it and returning to it?

Intentionally abandoning prayer is one of the greatest sins. What helps in maintaining it are: contemplating the enormity of the offense, associating with the righteous, persistently and sincerely supplicating, striving against oneself while recalling the words of the Almighty: "And those who strive for Us - We will surely guide them to Our ways," maintaining some supererogatory acts of worship, and staying away from distractions and discouraging factors, such as associating with evil companions.