Many meditations are guided journeys for giving us a framework for a mental activity. This is great. It can lead our emotions and body to follow.
Others are designed to be more free flowing so that we can be aware of the habitual thought patterns that dominate our thinking lives. This deepens awareness of what we are - and what we are not, and opens us to more paradoxical thinking. This is great, too.
Most of us start to meditate because we just want to feel better. We start with guided journeys because they can help us relax, many for the first time in ages. But after a while, many of us yearn for something more - or we have seen things or experienced things in that relaxed state that are interesting or new or have opened us up spiritually. That's when we make the switch to the sitting, silent, watching-the-breath type of meditation, although most of us will bounce back and forth forever.
If we are lucky, at some point, the desire to sit so that we feel better falls away and we start to sit for the sake of sitting. Not because it feels good or feels bad, although being joyful helps to keep us sitting. But because we feel curiously at rest or peace when we do.