Good question, the fruit of the spirit is ...Galatians 5:22-23
So odds are that spirit that makes you feel relaxed on sunday but then irritable afterwards if asked to do anything is probably a different spirit.
The Holy Spirit does speak to us, but I don't think it's a feeling, an intuition, or some esoteric experience; the Spirit speaks through His word. We hear God in the preaching of the Gospel, this is a matter of faith. Faith beholds God in the suffering and the cross of Jesus Christ; to behold God in faith is to see the friendly face of God in Jesus. Jesus who says, "If you have seen Me, you have seen the Father". It is the Holy Spirit who brings faith home into our hearts by the power of the word, that word heard in the preaching of the Gospel, that word connected in and with the water of Holy Baptism, that word connected and with the bread and wine of the Eucharist.
As such I would argue that looking to any interior "proof" or "evidence" or "experience" is looking in the opposite direction. One does not look into themselves, but looks outside of themselves--we behold the external and visible things of God, these are the things of faith. We cannot find God by looking inside of ourselves, God is found in the Cross of Jesus, God is found in His word, in the Scriptures, in the Sacraments.
How does one come to accept that the Scriptures are holy and inspired word of God? Faith. A faith that comes from outside of ourselves, by the grace of God, at work through the power of the Gospel, "For faith comes by hearing, and hearing by the word of Christ" (Romans 10:17). Thus the word of the Gospel is "living and active, and sharper than any two-edged sword, even penetrating as far as the division of soul and spirit, of both joints and marrow, and able to judge the thoughts and intentions of the heart." (Hebrews 4:12)
We must therefore be careful not to rely on our own intuition or reason, not because intuition is bad, or because reason is bad; but because neither intuition nor reason can bring us one step closer God. God comes down to us in Christ, God meets us in Christ, and He continues to meet us in Christ through the Gospel and through the Sacraments.
If we preach that man must come up to find God by his own power, then man is forever lost in the wilderness of himself. But if we take the Gospel seriously, we know that this isn't the case: we don't go up to find God, God comes down to find us.
The question is therefore never "Have you made a decision for Christ?" but rather, "Has Jesus made a decision for us?" And the answer to that question is a resounding
yes. God accepts us in Jesus. That is the Gospel, that is what saves us, that is what heals us, that is what gives us faith.
It is therefore not our job to convince others to believe as we do, but to be a people of Good News, that through the word God continues to liberate captive hearts and bring them into the freedom of His love and kindness.
This is God's work, not our own.
-CryptoLutheran