Re: Promising God?
I think we're best to say clearly, "With Your help I intend to do this/not to do this."
Breaking the promise isn't of itself a mortal sin as it was a simple promise.
I can't comment on what the acts themselves were as they are unknown to me.
Very often when we make such promises we are depending on our own will, which really isn't very practical or sufficient because we are desperate to succeed by our own determination.
It is more humbling to promise "I'll try my absolute best to do this, with your grace" We think that's not enough, but it is the best way for the human beings that we are
Jesus does have something to say about promises
“Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but fulfill to the Lord the vows you have made.’ 34 But I tell you, do not swear an oath at all: either by heaven, for it is God’s throne; 35 or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. 36 And do not swear by your head, for you cannot make even one hair white or black. 37 All you need to say is simply ‘Yes’ or ‘No’... Matthew 5 33-37
Basically it's not a good idea, especially for more scrupulous persons, to force vows on themselves. To make things worse, not only are they disappointed, but then they are full of guilt that makes it difficult for them to live in the awareness of God's love.
It is better to say, "Yes, with Your grace I am determined not to do this (or I am determined to do this). I am weak, so please help me."