How do I let go?

I'm laying here under my mosquito net... all quiet in the house...  I star gaze through the space in my curtains. 
the barking dogs that once kept me awake and felt so unsettling are now like lullabies. 
How a place so strange becomes so ...YOU... I'll never know.
A weekend pass from boarding... that's what I asked for today.  I needed to be with them.  I need them.  Maybe more than they need me. How do I let go?  warm tears flow. 
Tonight one said "your boys have grown into men."  I looked around and saw that it was true. Once skinny, small frames with broken English (Engrish) Now tall, strong, intelligent, loving. 
This place... so written upon my heart... and it will remain.   Every sound, smell, laugh.  I am a sponge, soaking in every last ounce of Zambian goodness... while deep inside I am wondering how in the world I shall ever let go. 
"I would have despaired unless I had believed that I would see the goodness of the LORD in the land of the living. Wait for the Lord.  Be strong and let your heart take courage. Wait for the Lord."   Ps 27:13-14