It is ok and actually beneficial to feel frustrated or angry. In the moment that you do, you will most likely find that it just shows up and you have no way of stopping it and this is ok.
You were born with emotions. Your emotions are on two spectrums of the scale: lower vibrating emotions and higher vibrating emotions. Some examples of lower vibrating emotions are frustration, anger, impatience. Some of the higher vibrating emotions are happiness, peace, contentment. It is important to recognize when you have entered the lower vibrational field. Recognize it. Move through it as quickly as possible and reach for a higher vibration to pull you from the hole that you are in.
Sure, you are thinking this is easier said than done, but with consistent practice, you will master switching from a lower vibration to a higher vibration in no time. You will find how this move to a more consistent higher vibration in your daily life will show you how much easier life can be when you are living a higher vibrating existence. So, the next time you are feeling frustrated, fearful or angry, recognize the emotion as soon as you can. Focus on it. Feel it. Then place your focus on something that is pleasurable and uplifting so that you can move from the lower vibration to the higher vibrating field as quickly as possible. Amen.