How do you know when desires turn into attachments

You know that, when you can’t control your senses. The senses, including the mind, are controlled by the intelligence. When the intelligence is weak, the desires and attachments of the mind take precedence over the intelligence.

Krishna says:

While contemplating the objects of the senses, a person develops attachment for them, and from such attachment lust develops, and from lust anger arises. —Bg 2.62

From anger, complete delusion arises, and from delusion bewilderment of memory. When memory is bewildered, intelligence is lost, and when intelligence is lost one falls down again into the material pool. —Bg 2.63

Srila Prabhupada explains:

One who is not Krishna conscious is subjected to material desires while contemplating the objects of the senses. The senses require real engagements, and if they are not engaged in the transcendental loving service of the Lord, they will certainly seek engagement in the service of materialism.

In the material world everyone, including Lord Shiva and Lord Brahma -- to say nothing of other demigods in the heavenly planets -- is subjected to the influence of sense objects, and the only method to get out of this puzzle of material existence is to become Krishna conscious.

Lord Shiva was deep in meditation, but when Parvati agitated him for sense pleasure, he agreed to the proposal, and as a result Kartikeya was born. When Haridasa Thakura was a young devotee of the Lord, he was similarly allured by the incarnation of Maya-devi, but Haridasa easily passed the test because of his unalloyed devotion to Lord Krishna.

As illustrated in the above-mentioned verse of Sri Yamunacharya, a sincere devotee of the Lord shuns all material sense enjoyment due to his higher taste for spiritual enjoyment in the association of the Lord.

That is the secret of success. One who is not, therefore, in Krsna consciousness, however powerful he may be in controlling the senses by artificial repression, is sure ultimately to fail, for the slightest thought of sense pleasure will agitate him to gratify his desires.