Life is both easier and harder when you are young. You are good looking (but feel you are ugly). You are full of the certainties of youth (but doubt yourself). You come across beautiful women every day (but cannot talk to them anywhere).
Most pick up theory assumes a young lifestyle. Much of it is based around nightclubs. These are brutal environments where a beta male has his status slammed in his face over and over and where his raging hormones compel him to remain.
There are two main factors that determine your success or failure if you are over 40. The first is opportunity (the number of available women you meet). The second is identity (the desirability of your life.)
Opportunity is quite simple to engineer. Simply develop a social life. Go out often and always go to new places.
Identity is a more subtle thing. You need to ask yourself why a woman would wish to have your life. Is your life an adventure? Are you well traveled? Are you genuinely interested in many things?