A vital component of any kind of relationship is trust. Nevertheless, even if you have a close relationship with someone, trusting them is not always simple. 
Thus, those who struggle with trust They typically observe it in their closest connections, including those with spouses, family members, and close friends. In these situations, it may lead to problems in the relationship since the lack of trust ultimately leads to damaging thoughts, feelings, and behaviors that create suspicions, envy, and unfavorable perceptions of loved ones.

2. The Fear of Being Vulnerable 
Being vulnerable is a prerequisite for trust, and vulnerability can be unsettling or even hazardous for many individuals. By discussing your ideas, feelings, and anxieties with someone, you're opening yourself up to possible rejection or condemnation. 
It might be challenging for people with trust issues to build deep connections because of this fear of vulnerability. To prevent being harmed, they might instead maintain their emotional distance. 
3. Low Self-Regard 
People who have poor self-esteem frequently find it difficult to trust other people. You may think that people will ultimately notice your perceived shortcomings and leave you if you don't feel worthy or confident. This can cause you to constantly question if people genuinely care about you or are looking out for your best interests. 
Trust concerns may surface in these situations.

Not everyone is ready or willing to take the chance of exposing themselves, and this can be a hefty ask. They could find it difficult to trust that people would act honorably or meet their expectations, which lessens their willingness to be authentic. 
Sometimes a lack of trust is more about people in general than it is about the other person. Our capacity to trust other people in society is a component of generalized trust. Therefore, not being able to trust anyone at all is a sign of a lack of broad trust. 
This kind of trust is crucial for fostering a sense of community and social functioning. According to research, it also offers advantages for each individual, such as improved health and happiness.

You keep a specific distance from other people: individuals may have anxiety when opening up or approaching new individuals, despite their desire to do so, according to the Do Not Trust Anyone theory. Additionally, because they may feel exposed, persons who lack confidence frequently struggle to let go. 
Acts of jealousy: Generally speaking, jealousy is linked to a lack of trust, particularly in love relationships. As a matter of fact, studies have indicated that jealousy in partnerships is frequently caused by trust concerns.