Simplicity means sensible naturalness of the way of life and behavior, as well as modesty and lack of arrogance and self-importance. Simplicity is a pre-requisite of Love. It is also the indispensable tool of spiritual warriors, which God wants us to be.
The best way to develop simplicity is keeping close to nature and learning how to attune to its harmony. Here, in the solitude of forests, fields and lakes, without make-up on the face, with no earrings, fancy synthetic clothes or even with no clothes at all — we can love the beauty of the Creation and the Creator, accepting help from God in the optimal way, expanding with consciousness in the beauty of the Creation and in the Holy Spirit.
Simplicity is also beautiful in expressing one's love to other people: in a smile, friendliness, tenderness and openness with friends.
But it is important to always have sense of proportion. For instance, walking naked among those who do not understand you and propagating your understanding of
"simplicity" in this way — this can only be called tactlessness; this cannot be called a harmonious and spiritual act.
The same principle can be applied to sexual relationships: the "simplicity" that leads to sexually transmitted diseases and unwanted pregnancies, as well as that which is connected with violence and egotism — is not what God wants from us.
"Spontaneity" in expressing and realizing all of one's whims, needs and desires, which is encouraged in some modern pseudo-spiritual sects and other organizations, also does not have anything to do with the true Simplicity.
Only the Simplicity of intelligent people who belong to the sattva guna and of those who have reached even higher spiritual heights is the true Simplicity.
People of the tamas guna under simplicity will understand either sugariness, or violence, rudeness, scuffle and lying drunk in the mud.
The true Smplicity is one of the elements of the "God training". It is not for those who are far from Him.