Accidental Relationship Sabotage

Why do people rush into marriage? Why do they rush into living together or rush to having a family?
Why do people hold off getting married, or moving in together,  why do people resist even being in a relationship in the first place?

The answer to both why we speed up and why we slow down is the same.  Fear.

The reason you avoid being close to someone is to avoid being hurt.
The reason you rush into commitments is because you're locking things down before that person can get away.

The same thing is going on in both situations,  we are trying to have power and control over over a situation to avoid possible pain.  The problem is "he who fears he shall suffer,  already suffers what he fears".
The problem is,  the more you focus on the fear and what you don't want to happen,  the more you feed the beast. It's like quicksand, the more you do to prevent the pain you're trying to avoid,  the faster it makes you sink into it.

I don't blame people for how they behave... If there was a countdown to putting your hand on a hot plate, in that time,  wouldn't you do actions to try and avoid that outcome?

Got a big decision and don't know how to choose?

Never make choices out of fear, make them out of bravery and you'll make the right one.
S. Phelps

How to protect yourself from mental attacks.

The hostility towards someone else stems from fear. Defending yourself won't work,  making them feel better may not and definitely won't in the long term. It's an individual security issue and they are trying to control the situation and make that fear go away.  Learn to be brave,  and learn to spot someone who isn't.  When you learn to do that, you will not take attacks as personal and prevent unconscious attacks on others.