Losing out on something is never a pleasant experience, but there are plenty of synonyms that can help to describe it. For example, you might say that you missed out on an opportunity, or that you forfeited a chance to succeed. You could also use words like fail, fall short, or come up short to describe the outcome. Other related terms might include let down, disappoint, or lose ground. Whatever word you choose, the important thing is to convey the sense of frustration, disappointment, or regret that comes with losing out on something important.