There! I fixed it!
I totally understand what this is trying to do. It's trying to remind us to focus on the positive things in life, to take stock of what we're grateful for, and to choose not to let the negative things rule our lives. But "Good Vibes Only" (and other sentiments like it) is often used to shut down and ignore the harder feelings of life.
Imagine how it might read, for instance, to a person in a season of deep grief: "If only good vibes are welcome here, *I'm* not welcome here."
Let's remember that our authentic vibes are always better than the ones we fake. So, if you're full of positivity today, you're welcome here. If you're full of doubt and frustration today, you're welcome here. If you're full of grief and sadness, you're welcome here. And if you're somewhere in between, you're welcome here!