It is unlikely that a full face lift would be the best option given your age of 33 years old. Since you mention that the only area where you notice sagging is of the forehead/brows, I believe it would be best to treat that area.
You may want to consider Botox to the forehead to correct minimal brow sagging. In this procedure, you would receive injections to relax the muscles that pull the brows down. If the sagging you notice is more considerable, you may be a good candidate for a brow lift.
This procedure repositions underlying tissue and muscle in order to get rid of creases and sagging of the forehead. Depending upon your needs, this procedure can raise the entire forehead, or just the sides via an incision to your scalp, just along the hairline. Also, you should note that a brow lift and face lift treat two separate things. A brow lift raises the position of the eyebrows and the face lift will lift the cheeks and neck. That is why a consult is best. During a consultation with a Plastic Surgeon, you and your surgeon should come up with a treatment plan together that addresses your unique concerns and achieves your appearance goals.