I suggest you play the White Mage Story quests. And make sure you read the detail of the story. It makes you understand why the healer role is very different from the others. It's unique enough that you aren't just playing to heal and watch out for the tank to top their HP up, Not just raising the DPS or esuna them when need. Sometimes healing takes more than just about press that one Cure, it takes insights, it takes a lot of forward thinking if you ever start playing Astrologian. Take every criticism. Just take every one of them and try them out. In such a way, you will play and see what works for you and what not. Sometimes it takes luck and skills in life, such too in playing. All said, you're playing a game. Don't take it too hard on yourself at what other people say or do.

Such in life... these watermelons aren't gonna change for you. Just eat it and then make sure it nutriently flourish in your gut and flush them down the toilet.