The apostle is talking about a spirit that has been “given [to] us.” It is identified here as a “gift of God” that can be “stir[red] up.” It is bestowed through the laying on of hands, as we see throughout Scripture. Paul says that God's Spirit is not about human fear. Later in this letter, he reproaches Timothy for being ashamed of the gospel message and of Paul. The younger man seems to have been in some danger of letting down and needed to be admonished to be strong and to endure hardship. All of this is part of the fear to which Timothy was apparently inclined.
Paul contrasts the frame of mind—the spirit—that would curtail Timothy's effectiveness with the Spirit given by God. Paul calls the latter “a spirit . . . of power and of love and of a sound mind.” As in I Corinthians 2:12-16, God's Spirit is linked with mind. If we are yielding to His Spirit, then our minds will be sound; they will be disciplined and self-controlled. Our minds will be sensible, sober, balanced, and restrained, and we will have wisdom, discretion, and solid judgment. Through the guidance of God's Spirit, our minds will operate in a way different from, and often incomprehensible to, those in the world, because we are being impelled by the essence of God's own mind, which is the absolute epitome of sound-mindedness and the opposite of the course of this world.
The Spirit of God is also a spirit of love. We can combine this with Romans 5:5: “. . . the love of God has been poured out in our hearts by the Holy Spirit.” Along with that, the first element of the fruit of God's Spirit is love (Galatians 5:22). Godly love is an action—doing the right thing toward God or another person, regardless of the personal cost involved. Its foundational definition is in the commandments of God. A fear of sacrifice—a fear of giving up what is valuable to us—comes from the spirit of the world, but God's Spirit enables us to love through doing what is right and trusting that God will work things out.
The remaining attribute listed here is power. It is the Greek word dunamis, which can also be translated as “ability,” “strength,” or “mighty works.” Dunamis is the capacity for achieving or accomplishing. The Holy Spirit gives a person the capacity for God's will and work to be done through him. But this is not a personal power. Even the miracles with which Jesus Himself is associated were actually performed by the Father (John 5:19; 8:28; 12:49; 14:10). Thus, the power of the Holy Spirit is the outworking of God the Father, rather than something we can use for our own ends.
It is critical to understand that the power of God's Spirit is under the constraint of the love and sound-mindedness of God's Spirit. In other words, it is not simply power for the sake of power, nor is it for self-gratification or self-glorification. The evident power in the Acts 2 account of Pentecost has given rise to churches that seek after similar supernatural displays, yet those displays are entirely divorced from the love and sound-mindedness of God.
People can seek this power for the wrong reasons, and it can be misused. Simon Magus tried to buy the power of God to use for his own ends (Acts 8:9-24), and even the congregation at Corinth had to be admonished because they were not using their spiritual gifts for the benefit of the Body (I Corinthians 12). In the midst of his discussion of God's various gifts, which are simply the outworking of God's power, Paul spends a whole chapter explaining godly love (I Corinthians 13), implying that the Corinthians' approach to those gifts did not include enough love or sound judgment.
He spells out that anything they received—such as spiritual wisdom or the ability to heal or do other miracles, to prophesy, to discern spirits, to speak in tongues, or to fulfill the office of apostle, prophet, or teacher—whatever the spiritual ability, God's Spirit is the source of it all, so there is no ground for boasting. The use of the power of God has to be constrained by the love and sobriety befitting the Most High God, so that He is the focus, not the individual.