Let's share mistakes and lessons learned?

Some of mine below:

Pricing

• I should've created a unique pricing point, telling the potential customers straightaway. I'll need to invest $x and everything will be sorted to you in x days

Potential client: “how much does it cost?”
Me: “It depends. We charge $x for 5 KPIs + set up + project for 5 KPIs”
Potential client: “How much is the set up?”
Me: “It depends, could take some hours to a few days”
Potential client: ”ok, I’ll have a think”

Market

• Focusing on one industry first would be advantageous and easier to discuss what sort of problems the product solve

Potential client: “What can I monitor with your product?”
Me: “Anything, any area of your company”
Potential client: “What industries are you focusing on?”
Me: “With work with any industry”
Potential client: ”ok, I’ll have a think”

Product

• Less is more

Me: "Well, I think the current customers will love this new feature. Let's implement it"
After months of implementation...
Me: "Hey users, here's a brand new feature you were waiting for"
Customers: "Well, let's see if and how we can use it"
Me, after next deployment: "Well, we actually removed the feature, as made no one was using it"

Would love to hear your mistakes along the way and lessons learned.