From a particular perspective, the answer can be:
The Holy Spirit
Out of God, Jesus, and the Holy Spirit, the Holy Spirit, while not necessarily third in power, is usually listed third in the list when being spoken of, the last of three.
While this is not meant to be a theological post, I will leave out the references, only validating claims.
With hopeful eyes, you gaze at me
Hoping to catch up
A Christian awaits the power of the Holy Spirit
Never do you really see
The drink that's in your cup
Often, a person neglects to take advantage of the present moment, a failure of character, as well as a lack of faith [in the power of God hence Holy Spirit].
You think that I've got all the answers
And for all I know, I might
The Holy Spirit does have all the answers, think about this not from the Holy Spirit speaking, but rather the perception of the Holy Spirit by a believer who lacks sufficient faith to grasp the omniscience of God. They "think" the Holy Spirit has all the answers, but can't fully grasp it yet.
I might have the cures for colds and cancers
But you have to give me the might
The Holy Spirit has the power of healing of all sorts. "Might" instead of certainty, because "you have to give me the might", which is due to the fact that the power of the Holy Spirit on Earth is limited by the receiver's faith to receive that healing, among other factors.
You never know what secrets I hold
The gifts and curses I bear
Since the power of God is infinite, a person can never know all the secrets held; there are gifts to the friends of God, as well as curses to the enemies of God.
Wait long enough, and you'll have been told
The knowledge I can share
With patience and perseverance, the Holy Spirit will impart wisdom and knowledge, although it may take some time for the person's faith to grow great enough to receive this wisdom.