Song of Songs 4:16.

What makes the difference between a fragrant and a dull Christian life?

The ministry and activity of the Holy Spirit.

Here, in the verse above, the maiden invites her beloved to her garden (heart). Jesus does not come to live in barren, unfruitful hearts/lives. At creation God put man in a pleasant garden to fellowship with Him. 

The maiden wants the spices from her garden to flow out (aroma). The life of Christ is pleasant. It must be transmitted from our hearts.

Spices-ingredients of the Holy Anointing Oil- Exodus 30:22-25, symbol of the Holy Spirit. Note the plants in her garden, 4:14.

 For the fragrance to flow out, wind is necessary - the activity of the Holy Spirit. The maiden invites the wind to blow upon her garden (a call). On the day of Pentecost, He came as a  rushing mighty wind.

Why North and South wind? Proverbs 25:23 (rain). The rain will dampen the fragrance. The Holy Spirit comes from the 'sides of the north' ,God's dwelling  place- Psalm 48:1-2.

The south wind stills the place Job 37:17.

'Let my beloved come.....' If our heart is a pleasant place Christ will come and rest there. He rested  in a garden before and after the Cross.

Pleasant fruits-Galatians 5:22-23, produced naturally by the Holy Spirit. They are 'His fruits' and  'His garden'.