Faith is a gift of God, a supernatural virtue infused by Him. (CCC 153)
Heaven is beyond our reach.
It is not a place on this earth so that we can walk, swim, drive, climb, or fly to it. It is not a place in outer space to which we may travel in a rocket, or even see with the most powerful telescope. No powers we possess by nature can reach heaven. None. No number of good deeds done is sufficient, because natural things just don’t and can’t bridge a gap that is supernatural. By its very definition heaven cannot be grasped by any means we might employ.
The Catechism reminds us of the fact that we are not left as orphans despite our frailties. God who made us knows that we cannot reach Him on our own. He who made us to be with Him knows that, left to ourselves, we can never be with Him at all. And so He gives us supernatural gifts (above all faith) so that in the strength of His gifts we really can reach the unreachable. The cry “Lord, I believe; help my unbelief” is a perfectly rational plea for God’s saving help.
Until we see this fact, the most that we can ever do is try to reach heaven on our own. But that is striving after wind. We must humble ourselves, acknowledge our weakness (to say nothing of our sins!!), and beg for God’s gracious help. Even then, the very act of begging His aid is a gift from Him, because we can never really do that until we accept the fact of our weakness and unworthiness, until we know that we can only reach God and can only be truly satisfied in and by Him. Until that day we will never come to Him at all.