If no context is given, there are two possible meanings. (The 3rd definition does not fit into this sentence). #2 Can be used as a sarcasm: "Aren't we proud today?" 1. feeling deep pleasure or satisfaction as a result of one's own achievements, qualities, or possessions or those of someone with whom one is closely associated. "a proud grandma of three boys" synonyms: pleased, glad, happy, delighted, joyful, overjoyed, thrilled, satisfied, gratified, content "the proud parents beamed" "we have a proud history of innovation" synonyms: pleasing, gratifying, satisfying, cheering, heartwarming; 2. having or showing a high or excessively high opinion of oneself or one's importance. "a proud, arrogant man" having or showing a consciousness of one's own dignity. "I was too proud to go home" synonyms: arrogant, conceited, vain, self-important, full of oneself, puffed up, jumped-up, smug, complacent, disdainful, condescending, scornful, supercilious, snobbish, imperious, pompous, overbearing, bumptious, haughty; "bulrushes emerge tall and proud from the middle of the pond" synonyms: magnificent, splendid, resplendent, grand, noble, stately, imposing, dignified, striking, impressive, majestic, glorious, awe-inspiring, awesome, monumental 3. BRIT. Slightly projecting from a surface. "when the brake is engaged, the lever does not stand proud of the horizontal"

It means that "we are happy" or "we are pleased" for example when you succeed,and your parents are happy,they say "we are proud of you" so that means they are pleased because you succeed ^___^ Good luck^___^