Have ye forgotten that true and radiant morn, when in those hallowed and blessed surroundings ye were all gathered in My presence beneath the shade of the tree of life, which is planted in the all-glorious paradise? Awe-struck ye listened as I gave utterance to these three most holy words: O friends! Prefer not your will to Mine, never desire that which I have not desired for you, and approach Me not with lifeless hearts, defiled with worldly desires and cravings. Would ye but sanctify your souls, ye would at this present hour recall that place and those surroundings, and the truth of My utterance should be made evident unto all of you.

Bahá’u’lláh, The Persian Hidden Words #19

Man's identity or rather his individuality is never lost. His reality as a person remains intact throughout the various states of his development. He does not pre-exist in any form before coming into this world.

Shoghi Effendi, Lights of Guidance, p. 536

Regarding your question concerning the passage in 'Seven Valleys' referring to pre-existence. This in no way presupposes the existence of the individual soul before conception. The term has not been absolutely accurately translated, and what is meant is that man's soul is the repository of the ancient, Divine mysteries of God.

Shoghi Effendi, Lights of Guidance, p. 505

The Prophets, unlike us, are pre-existent. The Soul of Christ existed in the spiritual world before His birth in this world. We cannot imagine what that world is like, so words are inadequate to picture His state of being.

Shoghi Effendi, Lights of Guidance, p. 504

The soul or spirit of the individual comes into being with the conception of his physical body.

Shoghi Effendi, Lights of Guidance, p. 504