People stop trusting you when you hurt them. If they believe you did so consciously and intentionally, then even more so. If they think you are a person who breaks their promises, doesn’t live up to commitments, manipulates them or speaks about them to others, they are skeptical about you.
In short, they feel hurt by your behaviour and don’t trust you with their feelings again because—if left in your hands—you could play with them. The more you break their trust, the more they distance themselves from you, either physically or emotionally by holding back their feelings.
How can you change things in this case? If you have lost the trust of someone, start doing things to gain it back one tiny step at a time. Spend time understanding their needs and meeting them. Clarify and set expectations early in the relationship to avoid disappointment down the road. 
Lastly, apologize sincerely if you made a mistake. Provide no justification for your behavior; just a promise to take care of things in the future.
Gaining trust back might be easier said than done. If your behavior has hurt them then your behavior needs to change for them to trust you. No amount of words can substitute that. When they sense your sincere commitment toward gaining their trust back they are very likely to give it to you.