How do you follow through for real?
Take what you gained through those mental images and use them as a source of strength and courage.
What you're doing may make you feel a little awkward or even guilty, but don't let those thoughts prevent you from doing what's right.
You may need to consider your own mistrust about people as if those thoughts were a 'person, a negative influence' if you don't have a real person you need to break from.
Real person or mistrust, whether they meant to or not, this person was blocking you from the life you were meant to live. So were your doubts. Maybe you had some good times as things were. Maybe they were there for you when you needed them. Maybe not.
That's beside the point. You're at a cross road.
To take the path to freedom and the life that is meant for you, you have to leave behind people - and thoughts - who can't or won't go with you or who would prevent you from going at all.
The other path is to remain with the person who doesn't care about your future and suffer the consequences. Doubt and mistrust offer the same bad outcome.
It's that simple.
Which path are you going to take?