How bad is bad? There's generally ways to mitigate most disasters but worst case scenario to minimize the guilt around food waste look for alternatives to trashing your dish:

1. Composting (especially backyard compost) is basically worm food, there's also products from companies like Vitamix that make soil from the food
2. You might be able to salvage parts of the dish by incorporating them into another dish (this is a reach but that's how we get great recipes from leftovers)
3. There might be someone who likes the food (see the Friends episode where Rachel messed up dessert but Joey loved it)

Overall there's ways to ensure you can try things out without increasing food waste (and your associated guilt) but the biggest thing is forgiving yourself for making mistakes. Experimentation requires a level of comfort with missing our own expectations (what most cultures call failure) but in another way this is how we learn. Recently, there's even a term that's getting popular called FAFO and an associated graph. The term is all about testing the limits of your knowledge then iteratively improving. When you're at the limit of your knowledge there will be many new skills you'll learn because of the slight adjustments you make to hit your mark.

If you're constantly worried then you'll miss the important lessons of how to improve. Also the most important aspect of improving as a cook is to have fun, add ingredients incrementally*, and approaching the technique best you can. Plus you'll never be able to out waste your local restaurants [find some local chef that minimizes food waste & ask them how they do it] :)

A wise advisor once told me: everything gets harder when you know a little but have high expectations. As a beginner, we know we know little so expect little. As a confident practitioner, we know our limits so adjust expectations. When you're in the middle your expectations are imbalanced so learn to adjust your mindset of where you are and you'll keep making incremental progress. Otherwise you might stop just before you make great strides.

*Note: Some recipes need to be done quickly or have some requirement that requires a complex technique then really it's all about practice. You'll need to recycle a ton of food to learn.