Dreaming about wanting to paint a plein air landscape but feeling rushed by the setting sun can symbolize a few things.

1. Unrealized Goals: The desire to paint but the sun setting could represent a feeling of not having enough time to achieve your goals or pursue your passions. It may signify that you have aspirations or creative projects that you wish to explore, but you feel like time is slipping away.
2. Pressure and Anxiety: The recurring theme of the sun going down might reflect anxiety or pressure in your waking life. You may be feeling overwhelmed by responsibilities or deadlines that prevent you from focusing on what truly matters to you.
3. Seizing Opportunities: This dream could also be a reminder to seize the moment and take action. The sun setting can serve as a metaphor for the fleeting nature of time, encouraging you to prioritize your creative endeavors and not let opportunities pass you by.
4. Connection to Nature: Since plein air painting involves being outdoors, it might indicate a desire to connect more with nature or to find peace and inspiration in your surroundings.

Consider reflecting on your current life situation to see if there are areas where you feel rushed or unfulfilled. This dream could be urging you to make time for your passions and to embrace creativity while you can.