The primary purpose of God putting his spirit upoy selected individual in the old testament is to EMPOWER them for a particular task. Also it is for a specific and special service design, arrange and approve by God.
The effect the spirit seem to have on the carrier upon relating with God is of two sides. Firstly. If he obeys and has a cordial, intimate relationship with God, he shall be lead by the God's spirit to do God's desire work. Secondly. If he sinned, the spirit leaves him and he shall be casted away from God's presence and the holy spirit be taken away from him