Most people expect that growth will feel good across the board. That becoming a clearer, more grounded version of yourself will improve every relationship you're in.
Sometimes it does. Sometimes the opposite happens.
What looks like “quitting” is often a very organized response. It serves a purpose. Specifically, it helps protect how you see yourself. If your system treats sustained difficulty as a threat to who you are, then leaving will always feel like the right move.
Most people assume that falling off means they lack discipline. That if they were serious enough, committed enough, or ready enough, they would simply keep going.
But discipline isn't what separates people who follow through from people who don't.