The human body is a complex piece of machinery. One thing our bodies do pretty well is give us natural highs through the release of endorphins and other brain chemicals, it's part of the reward center of our brain. During intense emotional states or positive emotional experiences can trigger an endorphin rush or other body high.
When I was younger I often associated these natural highs with the Holy Spirit, confusing certain feelings with God's presence. This often led me toward seeking these experiences out and often judging my status before God on whether or not I could feel that high or not. Sometimes working myself up into a highly volatile emotional state intentionally in order to "feel God".
As I got older, as my understanding grew and matured, and as my theology changed I began to understand that my experiences were not the Holy Spirit, they were biochemical responses in my brain. God cannot be reduced to a feeling or an experience. God's presence in our lives is about His word and promise, not what we feel or experience personally. We can know the Lord is present with us because He says so, not because we have worked ourselves into a state of emotional ecstasy.
There's nothing wrong with being moved, emotionally, by things. By music, by Scripture, by many different things; whenever I receive the Eucharist I am still moved, sometimes almost to tears. But God's presence is not my emotional response(s), God's presence is the objective truth and reality of His word and promise; the encounter with God we have (for example) in the Lord's Supper is not an encounter inside myself, but an encounter outside myself, because God is here present in this meager bread and wine which is, by way unknowable to reason, the actual flesh and blood of Jesus Christ our Lord.
I can trust that the Spirit is in me, because that is God's promise.
My feelings are mutable, fallible, weak, and say nothing one way or the other about who or what I am with and in Christ; who and what I am in Christ is defined not by me and how I feel or by my experiences, but by what God has done already, and has said and promised. And so I find that my hope and salvation lay totally outside of myself, in the Living and Incarnate Jesus Christ who was born, lived, suffered, died, and rose again--and Him and what He has done alone.
-CryptoLutheran