Awareness is a great key.
Non-stop awareness can help you to remain in a open state.
As soon as you lose awareness of the senses, return when you notice it.
Remain with your senses.
See the influxes. Know their impermanent nature. Everything is changing.
Observe. Observe your senses. Observe your thoughts, observe your emotions.
Don't identify with any of it. Observe from third-perspective.
Gain third-eye vision. ;)