There are some major mistakes that you can make that can really affect your makeup application. Here are a few of them:
1. Applying Makeup On Dry Skin. Always use a moisturizer according to your skin type under your foundation and also use a good Primer. The one I'm currently using is Benefit's Porefessional.
2. Makeup Application In The Wrong Lighting. The best condition for applying makeup is a warm or natural light source. Natural sunlight provides the most accurate reflection of your face, but for those cloudy days when fresh rays aren't an option, warm white light, like LED, is the next best thing.
3. Wrong Blending Techniques
Make sure when you are blending its with the proper brush. Also check out this website to get more detailed information on blending https://www.makeup.com/en-ca/how-to-blend-your-makeup