You ask a very good question and I don’t consider it flip or facetious at all.
It all begins with the person of the historical Jesus Christ. I read about his life, from witnesses who walked the earth with him. From this I must make a determination as to the credibility of those witnesses. Upon learning that these witnesses were willing to die through martyrdom rather than deny their testimony and, based upon the writings themselves, I decide that they are credible. I must then decide whether or not Jesus was who he claimed to be. Reading the witness’s account of what Jesus said and did, I decide that he is the Messiah, the Son of God, and that for no other reason but unfathomable love, he died for me (and for all) to save me from my sins.
Having decided that Jesus was who he claimed to be, I then look at what he did. He started a Church; not Peter or Paul or Joseph Smith, but Jesus himself. “And so I say to you, you are Peter, and upon this rock I will build my Church and the gates of the netherworld shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.”
(Mt 16:18,19)
He gave them all power: “All power in heaven and on earth has been given to me. Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, until the end of the age.” (Mt 28:19,20)
The voice of the Church is the voice of Christ himself. “Whoever listens to you listens to me. Whoever rejects you rejects me. And whoever rejects me rejects the one who sent me.”
(Lk 10:16)
Timothy tells us that the Church is where we find truth. “…you should know how to behave in the household of God, which is the church of the living God, the pillar and foundation of truth”.
(1 Tim 3:15)
That is why I know that the teachings of the Church are a good standard to to measure my certitude against. Christ gave his Church all power, promised to be with it until the end, gave the Church the power to speak in His voice and established the Church as the pillar and foundation of truth. Sounds like a pretty good standard to me.
The Holy Spirit then confirms in me what has been taught by the Church, the “pillar and foundation of truth.”
That is a far cry from relying on my inner feelings as the basis of my faith. In the Catholic Church it all comes together, the history, apostolic succession, the power of Christ himself and an intimate relationship with him through the sacraments. And on top of it all, the Holy Spirit confirming all that we believe and have been taught by the Church which we can rely on through those promises of Christ listed above.
Now, you will quickly claim that the Church fell into apostasy (for which there is not a shred of evidence, historic or otherwise) and therefore I am being taught error. Therefore measuring the truth of my “personal testimony” against the truth of the Church is using error as the measure. But you really have nothing with which to back up your claim. You are left with no choice but to believe your inner feelings which you choose to interpret as a “personal testimony”. You have no history to speak of, no proof of apostolic succession, no proof of “priestly authority”, only the claims of a man. It makes sense to me as to why the “burning in the heart” is so very important to you. It’s really all you have because you have nothing that can be proven empirically. If I tell you an angle spoke to me last night, can you disprove it? If I tell you that the Holy Spirit told me to become Muslim, can you disprove it? It is rather convenient, don’t you think? I prefer the Catholic approach in which I find no conflict between faith and reason.