I wish I could make decisions and then STICK to them.
Fe can help to find the passion to stick to a decision and persist.
But why, exactly ? Guilt ? Peer pressure ? .......
As dominant introverted judgers, INTPs may think that introverted judgment is a calvary, since they're mainly driven by a need for adapting themselves to their environment, while a huge bunch of extraverted judgers are dictating rules for everything, and shape an environment in their own image, a world where introverted judgers are judged as an hindrance.
But eh, the purpose of reasoning is to adapt our paradigms to the reality. An opposite behaviour is senseless, unless we're some sort of omnipotent gods. From that perspective, extraverted judgment is probably unhealthy as a leading judgment function, and should be used as an incidental tool to find the resources to protect one's environment from extraverted judgers' invasive behaviour.
Plus I somewhat suspect extraverted judgment to impede the global moral development, by pushing us all into exogenous relations with moral authority. Anyway, if someday I become a XXXJ, please kill me.
I will totally admit that I have INTJ envy. I really wish I could follow through, plan, and complete projects better. I wish I could make decisions and then STICK to them. I do find most INTJ to be a little "dour", but I would probably have P --> J reassignment surgery if I could!
The point is, the part of myself I'm always vowing to change is really not something that I can change, probably.
You gotta want to do it. I don't mean change, I mean the task/trait that you want to do/obtain, without the desire to finish it just won't happen.
Work to your strengths. If you find motivation and finishing things is something you struggle with then search till you find something that can do that for you, it may have to be outside of yourself. Figure out exactly what stops you: Distractions? Loss of interest? Lack of focus? Laziness? Then work out what happens different when you actually do finish something and recreate that environment.
I'm craphouse with finishing everything I start, I start way too many things for that to even be possible but when something comes along that I want to, or have to, complete it's a matter of setting in place an environment that encourages me to finish, that means no tasty distractions, and some checks in place that will hold me accountable if I don't finish, pressure from other people is especially motivating in that respect.
Too much focus on "I'm an INTP" will be counter-productive as you can easily claim that you can't change part of yourself when that's the one thing in life you have the most control over.
As a scorer of 100% P in most cases J has always seemed like a mystery to me, it never looks more efficient and despite what most people think I've always found P to be a faster process
Take a clean room vs dirty room for a simple example, I clean my room significantly less than a J which saves time, I also know where things are located straight away cause they are exactly where I left them, I clean when its absolutely required not "just cause" although a simple example this spills into a lot of different aspects
There are many other examples and there have been threads on this before if you are willing to do a search where I have rigorously debated against this idea that P is somehow inefficient