Sometimes some activities have this effect such as spending time with animals or children, with close friends, or in nature. Sometimes it is helpful to listen to, ponder on, or look at the Names of Allah. One could also simply sit and spend some time in the darkness and see if an inner light eventually emerges. Shedding tears for Imam Husayn (A) likewise often has this effect.
Everyone's heart is different, some hearts are more naturally open than others, and sometimes it also depends on our current situation in life, as sometimes we close our hearts to cope with challenging situations around us.
I am sure there are other responses too that will be helpful.