You worry less when you're over someone since you're not as emotionally attached.
If you're embarrassed or humiliated to be with your lover, that's an indication.
A major red flag? You compare them to every possible mate you could have without them.
Love involves being attracted to someone, therefore if you stop wanting sex, you may be falling out of love.
Dating is fun for making memories with a partner. Thus, it's a clear warning sign that you no longer want these unique moments.
Do your arguments cause greater conflict? That indicates a worsening connection.
Do you daydream of vacations, relocation, or jobs without your SO? Then your relationship may not last.