More exercise

Really this cannot be emphasized enough. There is a physiological explanation for why those who intensely exercise feel good: endorphins. The word endorphins is contracted from endogenous morphine; they are endogenous opioid neuropeptides and peptide hormones which act as an opioid receptor agonist in the brain. That is one reason many exercise lovers report feeling compelled to exercise. This reaction can help with overcoming negative thoughts and generating positive ones.

Exercise can also act as a meditation in which the brain can clear itself of 'cluttered' thoughts.

Of course peoples bodies vary widely so it is important to find a suitable form of exercise. Swimming can be great for those with larger frames due to the support it gives. If running is difficult consider a long walk ;you could also consider starting a running routine with very short bursts of running.

I find that rewarding myself after running with coffee and food helps motivate me.

A key benefit of exercise is the fitness of the heart. As you exercise more the heart muscles are strengthened and the resting hear rate lowers; the heat becomes more efficient needing fewer beats per minute to do its job.

A key point is to gradually increase fitness. It can be dangerous for those with heart disease to exercise too intensely. Resting if injury occurs whilst exercising might mean a swifter recovery.