“How will I manage to keep up my activities if the baby wants to feed all the time?”
Perhaps the first thing we can tell you is: your life after having a baby is not supposed to be exactly the same as the life you had before. And that doesn't mean you have stopped being yourself.
In the first few months, your baby needs a lot of closeness and, if you are breastfeeding, it is to be expected that they will feed frequently and without rigid schedules. Perhaps, because of this, the question doesn't have to be “how can I keep doing everything like before?”, but rather “how can I adapt my life to the needs of this phase?” Some activities will continue, others will need to be adapted, and some can simply wait.
Six months can seem like a long time when looking ahead, but it is very little compared to a whole lifetime. You don't have to stop being yourself to take care of your baby, but you also don't have to demand of yourself that you keep living at exactly the same pace. This phase is not forever. It is just a small part of your story.