There are dogs trained to fetch things for disabled people; sense seizures before they happen; allow a disabled person to lean on them for support, etc. But, in regards to supporting your emotions, this will be a pet who has bonded with you. This relationship has existed between human and pet for centuries. You buy the pet, care for the pet, and if you are lucky the pet will appreciate this care and attention, and be your companion and friend. Animals are pretty smart in knowing how to keep a good relationship with someone who helps and provides for them, and also bond with certain people. The problem is that they are usually the ones who decide who they ultimately bond with.
Go to your local shelter and pick out a cat or dog who seems to bond with you, and adopt it. Be sure your personalities seem to match. If you like a lot of activity, pick a more active animal. If you like to sit and cuddle, find one who seems more cuddly. But, don't put too many rules on it, but find one who you are drawn to, or seems drawn to you.