Bhakthi can be said to be in its full form if all concerns about status, wealth, fame, relations, intellectual excellence and ones own body vanished and only true love for God remains. "Thannai maRan^dhAL than nAmam kettAL, thalaippattAL naN^gai thalaivan thALE" (She forgot herself, she even forgot her name, all she knew was the Holy feet of God) of ThirunAvukkarasar just says what is Bhakthi. There are a lot of such devotees. But two of them become the example of Bhakthi when one wants to talk about that.
The only son of the chief hunter, ThiNNan, came to kALahasthi while chasing a pig with his friends. He saw the Shiva Lingam atop of the hill. From that moment he forgot that he was a person who enjoyed great respect in his community, he was the only son for his parents, he forgot his friends who preferred going back. All his concern was "Oh! In this dense forest this kudumiththEvar (name of Lord Shiva in kALahasthi) is alone. There are a lot of wild animals here. Who is here to protect Him ? Who will take care of all His needs ? So I will stay back with Him" and he stood all the nights with his arms near the Shiva Lingam. God is the ultimate protector of each and every life. ThiNNanAr out of his love started 'protecting' even God. God do not have any need. But for His hunger ThiNNanAr brought the best tasted dishes that he knew, flesh of the wild pig. Though AgamAs say offering flesh is not correct, ThiNNanAr offered what he knew to be delicious. Lord Shiva didn't care about the flesh he brought, but he cared much for ThiNNanAr's love. ThiNNanAr became kaNNappar when he offered his eyes to heal the wound in God's eyes, which He created to show the greatness of kaNNappar. There is no surprise ! kaNNappar got the mukthi in just seven days which the rushis and yogis try hard to get all through their life, and he was offered a place by God to His right. He is praised by many great saints including shankarAchArya, mANikka vAchakar , thiru nyAna sambandhar and nakkIrar.
When people learn a things they generally develop a ego, though they survive a lot other hurdles on the way of reaching God. This results in the loss of dedication for God. SrI pArvathi Herself came to earth to show how people with great knowledge should act. When the Lord explained to pArvathi the Shiva Agama, She wanted to pray the God as it is said in the Agama. She came to kAshi and did a lot of Dharmas as annapUraNi. Then she came to kAnchi as kAmAkshi, made a Shiva Linagam out of sand on the bank of river kambai, and prayed the Lord according to the Agama rules. One day to show the greatness of Bhakthi, He created flood in the river kambai on the bank of which pArvathi was praying Shiva Lingam. PArvathi being the Adhi parA shakathi could have stopped the flood, or She , being the part of the Supreme, could have thought that "God is almighty and nothing can hurt Him". But Her flow of Bhakthi - love- for Lord was much greater than the flood in river kambai. She embraced the God with Her hands and body to 'protect' Him from the flood. That is the height of Bhakthi. What else can God do than appearing from the flood of Her Bhakthi.
The true Bhakthi is one when you surrender yourself to God completely and you have nothing for you, but everything for the Lord