On Stack Christianity, a specific question gets specific answers. You specifically asked "WHO decides whether I go to heaven?" not "WHAT decides whether I go to heaven?" Your specific question would get concentrated answers as to why God determines who gets into his heaven. After all, it's his dwelling place (Deuteronomy 26:15; Psalm 46:4; 1 Timothy 6:15-16)! There are unlikely to be many answerers here who would disagree with God being the one who ultimately determines whether you (or anyone else) gets into heaven. Granted, some denominations think a particular person who they say founded their group will be delegated that task, but the Bible is clear that it is only Jesus Christ who judges everyone (John 5:21-23).
However, you then immediately introduced that different question, as to WHAT determines entry, by providing the link for The Coastal Courier article about that. Then you referred us to the Quora page which goes all over the place with random answers and a whole raft of related questions. That page is all about peoples' opinions, and often descends into arguments between people with differing beliefs.
Stack Christianity actively discourages that kind of thing. Focused questions are encouraged, with laser-like answers sticking to the point. This means that your question at the top is clear, and so is the related one in your comments, "But if it's me who decides, why can't I just decide that I'll go to heaven regardless of whether I follow the gospel?"
My answer to those two connected questions is simply this: God has revealed to humanity in his written word what heaven is all about, and why it is not open to all people, after they have died. In particular, in the last book of the Bible, he has used pictorial language to point to a future day when all the living and all the dead will be judged before the great white throne, some being cast away, others allowed in (Revelation 21:11-15). There is far too much in the Bible about this to put into an answer here. Much of what Jesus said, while on earth, deals with the kingdom of heaven and who get in and who are kept out.
As the risen Christ is the judge before whom all will stand for judgment, and the gospel is the good news of Christ (what he did to open up heaven being one aspect of that), then to know WHAT is required by God and Christ to get into the kingdom of heaven would entail studying what the Bible says about all of that. But that, as I have pointed out, is another question! Grasping whether there's any link between that and human free will cannot begin until first God's authority and God's requirements are believed.
Once your first question is resolved, then the second question you raised is settled. No human decides for themself! The reason why believing and obeying the gospel of Christ is so vital follows on. Only then can the question of free will be tackled. But referring us to those other sites is just muddying the waters. Hopefully, other answers will go more deeply into God being the one who decides who gets into his heaven.