Tifa is great at being an AVALANCHE member. When someone is down, count on her to cheer you up, or make you feel better. Tifa helps Cloud find his true self, a plain old Shinra soldier, and realizes Cloud forgot since he was too embarrassed to tell anyone. Why? He wanted to be part of the "cool" or most recognized group, since nobody used to play with him. Tifa met him and made him promise he'd protect her when she was in trouble, because Cloud claimed he was leaving to join SOLDIER, with cool strength and power. If she found out he failed and became a Shinra soldier, he would be humiliated, so his lies confused him. Tifa, helped him gain his truth at the lifestream.
But, though he wasn't a SOLDIER, he still kept his promise.