I myself faced this dilemma (trade or invest) a lot of times. Let me summarize what goes on in my mind.
You read a lot about multibaggers,etc how you could have made 30-40 times your money in 3-4 years if you dint sell after making 30-40% profit(investing)
Then you have a stock which you bought at 100 that went to 150 but you wanted to be an investor so you held on but it goes back to 50. You feel like kicking yourself for not selling at 150.
I read all rules like :-
1) Sell when price-value gap is narrowed
2) Sell when growth stocks are quoting at ridiculous PEs
The rules look fine very very difficult to implement.
What I am doing is below :-
1) Have 2 SEPARATE accounts for investing and trading.
2) Unless really bad things happen to a company or PE is ridiculous ( not just high but really ridiculous), dont sell stock from investment portfolio for atleast 1 year. This brings in some self-imposed discipline. This portfolio is where I expect a few multibaggers somewhere down the line.
3) My trading portfolio.
Never trade the stocks that are in investment portfolio
I had a pre-determined amount in my trading portfolio.I have no intention to ADD anything to it
Periodically, whenever there is some good amount of profit, I use HALF of the profits to add to my investment portfolio. This is how I try to fund my investment portfolio.
Now trading does not mean I do anything on margin or follow technicals. Generally I play for only bouncebacks or ranges. If any frontline stock (not penny stocks) is beaten down say 20-30 % based on rumour/news, I buy some. If it falls 10-15% more, I buy more. Then I sit tight. Usually I end up with a profit of 15-20% in a few days/weeks and I take it home.
My process seems to be working ok for me since the last year or so. If anybody has any similar process, then it will interesting for others to hear about that.