You have upper eyelid ptosis.
There is no nonsurgical method for addressing this. It requires a surgical repair. It will brighten your appearance and I think you will be very happy when you are ready. See a fellowship trained oculoplastic surgeon. The American Society for Ophthalmic Plastic and Reconstructive Surgery maintains a regional directory on their website that can help you find a well qualified surgeon in your area.
Treatment for sad eyes
Thank you for sharing your questions. You have ptotic eyelids (droopy) which can be lifted with one of several methods by an experienced Oculoplastic Surgeon. You might also benefit with some Restylane injections into the lower eyelids and cheeks. This will help to raise the lower eyelids and enhance the bone structure around your eyes.
Cure for sad eyes?
The best non-surgical cure is a SMILE. (This brings the cheeks upward to help support the lower lids.) No one will think you are sad or dull if you have a smile. In my opinion, surgery would not be appropriate for this.