Getting Cold Feet?

I have been getting quite a few jobs lately, very busy and happy. However, it is obviously adding me more stress. On 1 hand, it shows that clients believe in me therefore passing me more jobs. On the other hand, I fear of failing or disappointing them in any way. As you get busier, you tend to neglect certain details or take for granted some stuffs. I very much wanted to do more but as we all know the maths, by doing more also means chances of mistakes also goes higher.

I have attended quite a few seminars or courses by now and knowing that being a sales person, you have to take away the personal role of yours away, by not being affected personally on comments at times. However, being passionate in my industry, I LOVE what I do! How to remain unaffected at times?