Do we have to feel everything? Can we just feel joy all the time? Surely! Human consciousness is evolving. We are all pieces of a greater whole. We each represent a single point of consciousness on the graph of total human consciousness. There are people today and in the close and distant past who have reached an enlightened state of being, so we know that it is achievable. These people, like Jesus, Buddha, and a variety of yogis have reached an enlightened state of being. They experience life differently. For example, a yogi master who can sit for hours in a state of total bliss.
So what if we are still experiencing negative emotions? The first step is to accept the way we feel. When feelings come up, we can allow ourselves to feel that way and accept that is the way we feel. Afterwards, we can instead choose not to identify with the feeling. We can move from wishing things were different to accepting things as they are and finding peace in the perfection that is our world. Said another way, we can either choose to create problems in our lives, or to find solutions.
What about when we have passed this step? Then we move from acceptance to joy by living joyfully in the now. When we find what we love to do, then every day is a gift. The mind's natural state is peace. If we give it the conditions to carry on that way, then it surely will.