Often labelled a thankless job. A tpm must often times be responsible for all facets of a program without direct reports and individual delivery. In this process a TPM is dealt with many challenges such as dealing with a plethora of personalities, forging relationships with said personalities and gaining influence, resistance go delivery milestones, keeping the team organized, having to advocate for the body of work at an executive level and so on. 

I'm a TPM myself and have had various roles in various companies along the way. Each differing vastly from eachother and in various industries. Im on the journey of being the best that I can be, but sometimes it's hard to get good feedback until you leave a company and they're sad to see you go because of what you provided. It also feels like there is a lot of resistance to TPMs whenever I have started new jobs, which always makes things challenging and leads to a lot of internal doubt for me personally at the beginning of jobs. Happy to hear what my fellow level-ers think about this topic.