Sounds like a positive dream. Consider that a messy lawn is a cluttered mind or area of life, and a locked and unwelcoming gate is an inability to gain access to or fear of something needed.
You had full control of the welcoming gate, unfastened and allowing you full access to the lawn, which you tended to, bringing clarity and satisfaction. I would guess that you are finding peace in some area of your life, and that continuing what you are doing there will bring more positive results. You have control over the situation, which suits you. If by any chance, however, your garden isn't as satisfying as the lawn beyond the gate, you may wish to consider how you can improve it. It may be that you are giving a lot of love and attention to an external source, neglecting your own garden in the process. But otherwise I'd say it sounds like a very positive dream.
Just my impressions. Maybe some other interpretations from other members will give some other insight.