Life is a reflection of action. To run around here and there without any concrete output leads to a meaningless life. If you just cruise along, you will waste most of your time and energy without adding any significant value to your life. In the absence of goal, your mind will easily get involved in useless thinking and gossips. The fact of the matters is that being engaged in any activity at the given period of time, which are not directed towards the realizations of your life goal, will waste crucial parts of your life and that in turn fill your mind with regrets in later stage of your life. So to have a sense of achievement and be happy in life, you should lead a meaningful life.
The secret of leading a meaningful life lies in setting yourself a goal. While setting your goal, it is utmost importance to be sure where your passion lies and what you want from your life. Do not set your goal in a hurry and refrain from satisfying someone or feeding your ego while finalizing your goal else it would be counter productive. Everyone has different set of skills, expertise and passion in life. So figure out your own strength, skills and passion and set your goal accordingly.
Once you finalize your goal and road-map to realize it, you should stick by them for the certain period of time but not always. In this changing world, no plan could be hundred percent perfect. With each passing day's situations and circumstances get changed around you. So you should review your to-do list regularly to fit in the changed situations and circumstances. The chances are that, by reviewing your to-do list at the regular interval; you can realize your goal smoothly and early.
To conclude, achievements are yardstick for leading meaningful life. Set yourself a goal, review your to-do list regularly and keep shifting your goal post to measure your life by achievements. The biggest reward of achievement is a sense of self-worth, which generates never to end happiness. So lead a meaningful life for unending happiness and abundance in life.