The following words of Skanda from "Shree Skanda-Purana" are very crucial from Tantrik point of view (in Tantrik Traditions Puranas are often interpreted in Tantrik Light).
So, Skanda speaks not only about abandoning Bhagavan Shree Vishnu, but about abandoning Tantrik Sadhana.
As you know, once a sadhaka gets Mantras and other Amshas of Sadhana from Guru, he should never deviate and abandon. In case of sadhana abandoment, curse and subsequent adverse births ("state of life" as Skanda says in the cite) are "earned".
Though, good news - you will hardly find a sane Tantrik person falling from his sadhana even in Kali-Yuga, because Tantrik Sadhana stipulates very noble adhikar and The Protection of Shreemati MahaLakshmi-Devi and Bhagavan Shree Vishnu.
And in Our Sampradaya (Shree Ramanuja-Sampradaya) we are especially protected by Shreemati MahaLakshmi-Devi and Her Kavacha.
