Let's examine some examples you'll find all over the internet.
Maybe you are physically sick. You can still be happy right? We all have experienced that before, being happy and sick at the same time.
Maybe you've killed someone years ago and you're still suffering about it. You are suffering from your ego. You are suffering from the look of others (including yourself).
Maybe you've lost someone and you're still suffering about it. You are suffering from the fear of death. And your ego. You want to control your environment and you don't feel whole. You dont have gratitude.
That prerequisite is well known and documented all over the internet and in books. The problem is: the proposed cures dont work. For some reasons we might understand later in the discussion, meditation for example will get you nowhere (or not very far). But the following might.
---------------------------
Ask yourself the following question once per day for 5 days: is it pleasurable in my head right now?
There is quite some subtleties at play here. Since this is HN, I'll be happy to discuss them with you even though it's better you experience them yourself.