Give yourself a month of 3 days a week, 25-30 minutes each session to allow the tendons, ligaments AND muscles to adapt before increasing frequency, intensity, or duration. Enlist the help of someone who is knowledgeable and can help assess your current fitness levels and suggest exercises and activities that will work best for your lifestyle, preferences, needs, and fitness goals. Remember that it's cumulative movement that counts most over the long run. In fact, find several. Making a commitment to someone else usually helps you keep on track for those days when you'd really rather do something else.
Nothing kills motivation more than doing the same workout day in and day out.
By doing this, you will reduce your risk of injury and will see better results. By taking incremental baby steps each and every day and accomplishing your goals, you'll gain not only the body confidence, but also the mental confidence you need to accomplish wonderful things in ALL areas of your life.