Act as a UX optimization specialist for e-commerce fashion retail. Our target audience is millennial shoppers aged 25-40 who value fast checkout and transparency. Analyze our current checkout process and identify friction points contributing to shopping cart abandonment. Focus on mobile responsiveness, guest checkout options, and clarity in shipping costs. Propose 5 actionable improvements, prioritizing changes that address unexpected fees at checkout and multi-page form fatigue. Include metrics/KPIs to measure success (e.g., 15% reduction in exit rates on the payment page). Explain how each improvement aligns with psychological principles like loss aversion (e.g., limited-time free shipping) or social proof (e.g., live purchase notifications).