For many people, therapy is an important part of their mental illness treatment. Even for those of us who aren't doing therapy, there can be a lot of benefit from incorporating therapy-based tools. Mental Health @ Home has a number of posts describing these kinds of tools, and here are some of the highlights.
The post Therapy Tools for Mental Health provides an overview of some of these, including the vicious flower, behaviour chain analysis, decisional balance grids, and the worry tree.
Acceptance and commitment therapy has a lot of useful tools, including the life compass. ACT uses a lot of metaphors to help illustrate concepts (you can read more about ACT metaphors here). A favourite of mine is the leaves on a stream metaphor, which represents how thoughts and emotions come and go.
There are lots of free worksheets and workbooks available that incorporate concepts from evidence-based forms of therapy like cognitive behavioural therapy (CBT), acceptance and commitment therapy (ACT), and dialectical behaviour therapy (DBT). MH@H has a list of free mental health workbooks here.
The stress bucket model represents how we're affected by our capacity to cope (the size of the bucket), the stressors coming in, and healthy coping mechanisms that can release stress. It also represents unhealthy coping mechanisms as essentially siphoning stress back up into the top of the bucket. To most effectively manage stress, it's important to try to control the stress coming in, find coping skills to release stress, and avoid using unhealthy coping mechanisms.