Happiness can be hard but there are a few ways that help.
First, pray and ask God to help you get over any anger and bitterness you have toward the wts and toward any people, whether from the JW's or anyone else.
Work in harmony with that prayer. Whenever some resentment arises, catch yourself, admit that you are not acting in harmony with your prayer, tell God "woops, I'm sorry", and make yourself stop thinking about it. It's a little tricky but it can be done. By pushing the negative thoughts out, it makes room for love to consume you.
Pray for faith in Jesus, more than you already have. Pray for understanding about what it really means to follow Jesus. Read the gospels and all of the New Testament. Tell people about your faith, but not in an arrogant way, but just to testify to your faith. More importantly, be Jesus. The world doesn't have Jesus, as a person, on earth. So we have to be Jesus for them. In our thoughts, and our actions. If we think about things that upset us, we will be upset. If we think about immoral things, we will be more immoral. If we think about material things, we will lust for pleasures like money, and we will not be content with having our needs provided for us.
What we think about, is what will consume us. So think about how Jesus was and is. And be that.
Thank God for everything in your life. When you overcome something, thank God for it. He deserves our praise. Whenever something good happens in your life, praise Him. When something bad happens, look at how you can handle it according to God's will. When you pray and ask God for help, believe that he is helping you. Even when you can't see it, he is helping. So again, thank Him for helping you. Always have faith. Never doubt.
That is how you can be happy. Real happiness.