Emotions come through the body, but both their generation and our response to them depend on choices in the mind. Emotions occur at a subconscious level, but the choices we make that influence their creation and dictate our response to them occur as conscious choices. A great deal of their generation comes from our past choices, and what we do with them thereafter is completely dictated by us.
How you feel about something is completely separate from what you do about it. As sentient beings, humans have the power to choose how we act based on our thoughts, no matter how we feel. It is possible to act to most fully advance your purpose even while feeling your worst.
Acting contrary to your emotions can feel as challenging at first as choosing to hold your breath while walking into tear gas: it is unnatural, you have to do it on purpose, and it is uncomfortable, but it is still obviously better than the alternative.
Often, it’s not enough to merely try to think differently. Contending with emotions can be a full body exercise. When you seek to feel differently than you do, engage in physical activities or go to physical spaces that are more likely to produce the feelings you seek. For example, when you are angry, you can do things that generate peace. When you are overwhelmed, you can do things that bring completion. When you are depressed, you can have some fun. When you are exhausted, you can rest.
The more you intentionally choose what is rational over what is emotional, the easier doing so will become. The more you practice rational self-control, the more you will find your emotions bending to your actions, rather than having your actions bending to your emotions.