Self-doubt galore!

Hi- so I’m struggling with having my own back.
I think I’ve been so dependent on others’ feedback that I rely on it to decide if something is/was good or bad.
Today I gave a presentation, for example, 15 people showed up (over 50 signed up). The organization sent out the handouts in advance.
I have no idea if it was helpful/useful.
I’m making the number of attendees mean they saw the content and didn’t want to attend. A few dropped off the call before the end. I am making this mean that they hated the presentation. Yikes. I have so much work to do on my thoughts that it’s overwhelming.
Where do I start?