Srila Thakura Mahasaya (Narottama Dasa Thakura) sings:

radhika carana renu, bhushana koriya tanu,
anayase pabe giridhari
radhika caranasraya, ye kore se mahasaya,
tare mui yau bolihari

“If you decorate your body with Radhika’s footdust, you will easily attain Giridhari.
I praise the great soul who takes shelter of Radhika’s lotus feet!”

The only means to subdue Sri Krishna is love and devotion.
The Upanishads say: bhaktivasah purushah. The limit of love is called mahabhava. Caitanya Caritamrita says:

prema krame badi hoy sneha mana pranaya;
raga anuraga bhava mahabhava hoy /
premera parama sara mahabhava jani;
sei maha-bhava rupa radha thakurani ”

“Prema gradually grows into sneha, mana, pranaya, raga, bhava and mahabhava. The highest stage of prema is mahabhava and goddess Radha is the very form of that maha-bhava.”

 Innumerable streams of the honey of maha-bhava flow from Sri Radhika’s lotus feet (see verse 94 of this book), therefore it is understandable that Krishna is wholly controlled by the dust of Her lotusfeet.
Srila Jiva Gosvami has written in his Bhakti Sandarbha (187):
prema taratamyenaiva bhakta mahattaratamyam mukhyam
“The more prema you have the greater you are.”

In his ‘Ananda Candrika’-commentary on Sri Rupa Gosvami’s ‘Ujjvala Nilamani (Sakhi-prakarana, text 6)’, Sri Visvanatha Cakravartipada writes:
sa ca prema jatya ananto’pi kvapi paramanu matrah kvapi parama mahan kvapi mahan kvapyapekshika nyunadhikyamaya iti catuh parimanakah/ tatradyo’jata ratikeshu bhakteshu teshu premno durlakshyatvat bhagavato’dhinatvam api durlakshyam eva. dvitiyo vrindavanesvaryam eva tatra premnah sampurnatamatvena adhinatvam api sampurnatamatvam eva….atha tritiyo vrajaloka eva tatra premno mahattvena adhinatvam api sampurnam eva na tu sampurnatamam…. atha caturtho naradadishu teshu teshu premanurupam adhinatvam.
“Although there are unlimited varieties of love, they can be classified fourfold according to their amount.The ordinary practitioners have an atomic amount of love, devotees like Narada Muni and others have love in greater or lesser amounts, the people of Vraja have great love of Krishna, and Sri Radhika, the queen of Vrindavana, has the greatest love.
Naturally, therefore, She also controls Him to the greatest extent.”

When Sripada says: tam radhika carana renum anusmarami
“I constantly remember Radhika’s foot dust”,
he aims at ashta-kaliya-lila-smarana, 24-hour meditation on Radha and Krishna’s daily pastimes.
This is the main item of raganuga bhakti, or spontaneous devotion. Without remembering God, the mind is lifeless and the dogs and jackals of lust and anger can freely play in it.
The sweetest meditation is that of Sri-Sri Radha-Krishna’s pastimes. One should not try to remember these pastimes according to a regular schedule. This is a dead and stale practise. The experience must be spontaneous.
An example is given hereby: One of the most famous Gaudiya Vaishnava saints in recent history was Sri Krishna Dasa Babaji. He was also called siddha baba (a saint who had attained perfection) and he lived in the town of Govardhana in the 19th Century. One day a devotee came to him, crying. When Baba asked this devotee why he was crying, the devotee said: “Today I could not do any bhajana (devotional practise)!
In the morningtime I (mentally) put a ring on Srimati Radhika’s right hand, but I became so absorbed in the sweetness of Her hand that I could not take my mind away from it anymore for the rest of the day (although he was supposed to proceed in his service according to the schedule of ashta-kalina-lila-smarana)!”
Baba was very pleased and he told the devotee: “Today you have really done bhajana!” This is called anusmarana or ‘constant remembrance’.
A devotee who constantly practises smarana can gradually attain such a condition.
The Gaudiya Vaishnavas practise devotion internally by remembering the transcendental pastimes of Sri-Sri Radha-Krishna and/or Sri Caitanya Mahaprabhu and externally by hearing and chanting about these pastimes.
Thus, at the time of death, they may be able to enter into the Lord’s eternal pastimes.
This is the highest perfection of life.

vedavakta padmasana, tantra-vakta pascanana,
suka, sri narada, bhishma kori.
deva nara munigana, ye harira darasana,
sahasa na paya dhyana kori

kintu ki ascarya suno, sei to purushottama,
nava ghana nandera nandana
radhika carana nidhi, paraga ye siddhaushadhi
yara sire kore darasana

“Neither Lord Brahma, the speaker of the Vedas, who sits on a lotus flower, nor the five-headed Lord Siva, who speaks the occult Tantra scriptures, nor Sukadeva, the speaker of Srimad Bhagavata, nor Sri Narada, Bhishma, the demigods, human beings or the wise men can easily attain the Supreme Person, Lord Hari, within their meditations.
But listen, how amazing! On the head of that son of Nanda, Who shines like a fresh rain cloud, one can find the foot dust of Sri Radhika, which is like a magic herb.”

tahara premete hari, apana vikroy kori,
avicare vasibhuta hon
ananta sakati purna, radha padapadma curna,
paramrita parama ratana

“Hari sells Himself to Her love and totally submits Himself to Her. The dust from Radha’s lotus feet is full of unlimited power and is the highest nectar and the highest jewel.”

bhane sri prabodhananda, radha pada makaranda,
darase parase bhagya hina
kunjesvari kripa koro, padarenu nirantara,
smarana koribo anudina

“Sri Prabodhananda sings: I am so unfortunate because I cannot see or touch the honey-like feet of Radha! O Queen of the bowers! I constantly remember the dust of Your feet!
Be merciful to me!”

– from Srila Ananta das Babaji´s commentary on Sri Sri Radha Rasa Sudhanidhi
– translation by Sripad Advaita das