One must admit, Paul didn’t make much of a “positive confession” in Romans 1:10, when he told the church at Rome: “if perhaps now at last by the will of God I may succeed in coming to you.”
Those words “if perhaps now … by the will of God, I may succeed …” are significant. They express a humble uncertainty, and a willingness to submit to the will of God, which he admitted was unknown and uncertain to him just then.
It is also significant that Paul didn’t seem concerned with trying to make a “positive confession” by saying: “I’m claiming it; I AM going to be coming to you!” Instead he humbly submitted himself to God’s will: IF it was His will, then he would be coming to them soon — but he allowed for the possibility that it was NOT God’s will, so he used the word “IF”.
Surely it is not wrong for us to do the same thing. We don’t need to “positively confess” anything which God has not assured in His word. We need to have the kind of humility about ourselves and our future which Paul modeled here. Only God knows what the future holds. We are not masters of our own fate. As James 4:16 reminds us, when we make strong claims about what we will or will not do in the future, “all such boasting is evil”. It is not wrong — and in fact as James again reminds us, it is surely very RIGHT for us to say, “If it is God’s will” then we will do this or that. (James 4:15)
Thus it is not wrong for a Christian to say things like: “If it is God’s will” and “Lord willing.” In fact, according to scripture, these phrases, and not “positive confessions” should permeate a believer’s vocabulary.