There are many things that a heavy workload can mean. Most of them are systemic, and have no connection to your relationship with your manager.
It would be wonderful if it were always true — that a heavy workload always happened because your boss thought you were competent, valuable, helpful, or otherwise saw you in a positive light. Sadly, that’s not the case.
A heavy workload could mean:
The business doesn’t have a clear direction. Instead of getting clear, you're asked to do a variety of different things that are more than any single person could do
Multiple people are prioritising things, meaning multiple “#1 priorities.” Similar to the above, but this time people are choosing directions independently, or are being set against each other by people who believe that competition increases effectiveness
Your boss is overloaded and is offloading work onto you
Your boss doesn’t care about your workload. Some bosses don't notice how much they're asking others to do.
Your organisational culture doesn’t value time to think. Constant reactions lead to more firefighting, and more reacting.
Your organisation rewards starting work, not finishing it. Over time, this results in more and more work on your plate, as if you're constantly at the beginning of a buffet and are never allowed to leave the line.
You’re seen as an order-taker. The thinking happens elsewhere, and you just deal with the results. Whether those results are achievable or realistic, given existing constraints, often goes unnoticed.
Another department has convinced a boss somewhere in the hierarchy that some part of what should be their job should be done by somebody else, but the company doesn’t want to hire more people. Now it's your job.
The company is too cheap to hire enough staff for the work they want done. There's always more work that could be done. Does the company draw the line somewhere, or are you expected to do it all?
The company has money problems and can’t staff adequately. Sometimes this is understood and accepted, as a temporary problem. Hopefully it gets resolved before people burn out.
Someone in your team left, and you picked up the slack, resulting in you working extra hours, while the company decided that burning you out is better than paying another salary.
It’s always worth remembering that the system (read: environment) in which you work has a huge impact on your experience of it, including your relationships with people around you, and your ability to finish work.
A system that cares about your wellbeing won’t overload you. It won’t put you under duress. It won’t coerce you. It won’t do things that encourage you to work weekends, or long hours. It won’t burn you out. And if you end up in a situation where you’re overloaded, a system that has been built by people who care about the people in it will respond by lightening your load, so you can do your best work.
Bottom line: a heavy workload is more likely to be a result of incompetence, indifference, or malice, than anything else. Because we look after the people we love and respect, we don't take advantage or abuse them.
If your workload is excessive, what do you think is the cause?