As part of imam al-Qushayri’s commentary on the Light Verse (24:35), he says:

“The light of the heart: it causes a continuous state of agitation which does not allow one to remain lazy. He connects his travel in the day with travel at night by the use of his reflection, and God nourishes him by the light of success so that no obstacle to his spiritual effort: of love of leadership, or the inclination to evil, or indulgence, can hold him back.

Then when the state of his forgetfulness becomes apparent to him, and he is able to see clearly his situation, knowledge will most certainly be obtained. Then he will continue to increase in certainty upon certainty based on what he sees in the his interacting with the states of contraction (qabd) and expansion (bast).

The reward and compensation is in the increase of unveiling upon the increase in effort, and the obtainment of ecstasy (wajd) when performing the litany (wird).”

- based on the translation of Kristin Zahra Sands, Sufi Commentaries on the Qur’an in Classical Islam, p. 130, with several corrections and changes.

Then she says:

“Al-Qushayri breaks through the common understanding of the metaphor of light here by focusing on its qualities of energy and movement. Rather than accepting the simple equivalence of light as guidance, he gives the unusual image of light as something agitating the heart.” (p. 131)

نور القلب: ثم موجبه هو دوام الانزعاج فلا يذره يعرِّج في أقطار الكسل، فيصل سَيْرَه بِسُراه في استعمالِ فكرِه، والحقُّ يمده: بنور التوفيق حتى لا يصده عن عوارضِ الاجتهادِ شيءٌ من حُبِّ رياسةٍ، أو ميلٍ لسوءٍ، أو هوادة. فإذا أسفر صُبْحُ غفلته،واستمكن النظر من موضعه حصل العلمُ لا محالة. ثم لا يزال يزداد يقيناً على يقين مما يراه في معاملته من القبض والبسط، والمكافأة والمجازاة في زيادة الكشف عند زيادة الجُهْد، وحصول الوَجْدِ عند أَداء الوِرْد.

So increase the light of your heart by any means possible, until you reach this state of agitation that pushes you forward so that no obstacle can hold you back. One way (possibly the easiest way) is to be in the company of the blessed. Shaykh Saleh al-Jaafari says:

من جاور السعداء يسعد يا فتى ** وتراه من أنوارهم يتورّع

And:

ومن أنوارهم نارت قلوبٌ ** رأيناهم ببعدٍ مظلمينا

The first line roughly means that he who resides near the people of felicity will be felicitous, and you see them becoming more wary of sinning because of their lights.

And the other line in another poem says about visiting the Ahlul Bayt:

“And from their lights, hearts have been lit *** which, when they were far, we saw them in a state of darkness”.