http://www.coping.org/relations/boundar/intro.htm
The above URL might be helpful in determining healthy boundaries in a relationship so that you can recognise such boundaries, set them and maintain them should you be in what is an abusive or controlling relationship.
One does not passively *trust* that a partner will not be "controlling" or "verbally abusive" whatever promises may be made and however contrite the emotionally abusive partner may be.
Rather, it is our responsibility to ensure we recognise what does and does not promote our emotional wellbeing and that we take steps to set and maintain limits to ensure our own emotional safety.
It is important to know ourselves and our limits and to clearly, clamly and assertively convey those limits to others and ask that they be respected.
Obviously, if a partner cannot or will not recognise our limits we must take steps to protect ourselves.
If we are committed to the relationship in question, then we may try avenues such as counselling to alter the destructive dyamics within a relationship.
However, if a partner is unwilling to confront the problems and to make lasting changes via intervention, then we must put an end to the relationship with an abusive partner for the sake of self-preservation.