If you have lost the ability to "trust" I think you have to take very small steps to rebuilding your capacity to trust.

Does someone meet you for lunch when they agree to on the phone, or not? If not, then I wouldn't trust them for much more (for example only.) If they do, they maybe you can trust them to run an errand for you, or call someone for you etc.

Does someone promise to have office work done for you by such and such a time, and never does? Then I wouldn't "trust" them until they can become consistent... maybe they are great at making phone calls as asked but not projects.

Does someone say they care about you, but fail to give you time to talk? Or do you know someone who listens intently but has never shared that they care about you? If you trust them enough to listen, maybe they will trust you enough to tell you about some of their activities/ideas? Work from there.. little by little.

Did I help at all? IMO you need to be able to trust a few ppl alot, and alot of ppl at least a little

For the last part...we often keep giving others a "second chance" even though we know better, because we WANT that relationship to work...and we really need to realize it is THEM not us, and to move on from there, imo Recognizing patterns in others who abuse is important, and then, going from what we KNOW in our heads, we need to NOT trust them if they fit the pattern, no matter what we really feel and NEED or want from the relationship. (No it isn't the last person who will ever speak to you or go out to the movies with you..)

TC This is a tough one.