Generate a full, in-depth guide for e-commerce owners on how to reduce shopping cart abandonment. The guide must be data-driven and actionable. It must include detailed sections on: 1. Diagnosing the Problem: Using analytics to identify drop-off points. 2. Technical & UX Fixes: A checklist of common issues like unexpected shipping costs and forced account creation, with solutions. 3. Psychological Strategies: A breakdown of techniques like using trust signals, creating urgency, and exit-intent popups. 4. Abandoned Cart Emails: A guide to writing a multi-email recovery sequence with templates. Please conclude with a disclaimer that continuous A/B testing is necessary.