ummm in my experience when you love someone but it doesn't work out then you get over them (rebounding) or as some people like to call it "moving on" depending upon the individual's own pace. Basically I have an emotional void that I'm trying to fill. The more I like the person the more I miss them.
All I mean to suggest is you built up your interest in the INTJ to be more than what it really was and your repeating yourself now with the ENFP. The reason is your dragging the past behind and not seeing true reality. Sounds like your searching for a solution rather than a companion. To be serious about anyone means your deeply committed to them. A contrary notion to 'there's plenty more fish in the sea'.
A optimistic point of view would be to imagine yourself happily married and the same for the INTj and ENFp and any other love interest (past, present or future) to be in the same situation. Therefore you eliminate any negativity or selfishness or self-pity. What I am suggesting is depending upon your on-look on life you can be happy with your ex, the INTj or ENFp but all you have to decide is what kind of happiness do you want? Happiness is expressed a thousand different ways and you can experience it differently with different people. So there is no such thing as the right or wrong person. Realisitically you can be happy with someone else and so can the ENFp and INTj.
My personal advice is make sure your happy no matter who your with and I do not mean having a malicious free license to be a bitch. Next, find a potential partner who is already happy so then you can only make your lives even more happier together.
That dreary sense of needing someone because their miserable without them makes no different. Really those people are miserable with people as they are without them. However when your a happy person you can even be happy with a miserable person but those moments maybe few and far between.