Your at that point in your life where you know something has to be done different.  Whatever it may be and for what ever reason you know it is time.  Most often it takes a big life event to shake us into  just considering making the changes we had put off in the past.  For some of us the event itself is enough motivation to jump right in and take charge and for some we need a little more help and a slower approach.  
I meet so many people that want to make the change.  They are so motivated at that moment and all with good intention, only to give up a few days in.  What most don’t realise is that making big changes in our daily lives takes time and the time spent transitioning will be smoother when we are actually not fighting or feeling we are denying ourselves.
The difference between creating an actual lasting healthier lifestyle for yourself and just creating a phase that will be forgotten next month is being prepared to do the ground work of letting go of old belief systems.  This my fellow humans is one of our species real challenges.   Lets face it, our habits are reflections into our social, cultural, environmental, educational and family belief systems that have been formed and followed by our sub-conscious mind.  Problem is as we grow up we also come to find these "habits"and "belief systems" are usually whats holding us back from actually growing.  There is an influx of information that is available now and most of it is contradicting and confusing.  We are now being told by anyone that knows anything that everything from the way we eat, sleep, move, think and breathe needs an overhaul.....Yep, and back to comfort zone we go. So how do we change?
We take it step by step and the rest flows from conviction and will power. We can not switch to positive mindset and maintain the flow if we are not convinced. And conviction comes from belief and in this case self belief is a must. The experiences that formed ideas and limiting beliefs passed on from our family, culture and education that have been accepted and stored also need to be gently rewired, this requires will power or our decisions and our ability to open up to new experiences will be over shadowed with caution, self doubt, fear and excuses. 
Know Thyself - Socrates
Start by being convinced and positive about the changes your making. 
Set small goals. Don’t over complicate or over commit. For example, this month I will get up and go for a 30 minute walk, 3 times a week and I’ll stop the soft drinks. That’s just two small steps which will make a huge difference. The following month take the next step. 
Structure: there’s that quote “By failing to prepare, you are preparing to fail”. If your going to make life changes than structure and preparation is a must. If your waking up a little earlier to exercise well you need to get to bed earlier. If your now taking your own lunch to work, make sure it’s prepared the night before. Set days and times for exercise. Setting your alarm and having your workout gear ready so your not wasting time at 5am looking for one sock.

Reminders needed: Out of sight, out of mind! Vision boards, Journals, Calendars, Post it notes, phone screen saver to name a few but keep a visual reminder of the changes and the goals you have set. 
Keep trying it’s never to late: it’s human nature to resist, it’s even human nature to look for the easy way out. Giving up and then punishing ourselves. But practice and belief in yourself can get you there. 
And most importantly surround yourself with positive people who support your goals. One step at a time, breathe, you got this.