In a startup, when should you execute and when should you plan?
There's no right answer.
But, I'm here to convince you of three reasons you should execute, instead of continue planning.
1. You aren't as vested in an effort you're planning as you are when actually executing an effort. That is the case for any investment (time or money). Therefore, you will allocate more attention to an effort when you're doing it than when you're planning for it. Do you follow the stock that you bought or the stock you had planned to buy?
2. Executing is the very next step; planning is too often just dreaming of what you see as your vision. Planning is important only for large milestones, which a newer startup should only have 1-2 per year (examples: pitching to a VC or making your first sale).
3. Execution is tangible: you can talk about something that was accomplished as a fact. However, with planning, you can only... well, do just that: continue talking about the plan.
Now go execute on something right now. Maybe it's buying your domain name, maybe it's reaching out to an old contact, maybe it's talking to that girl that swiped you right on Tinder. Maybe it's liking Handshakin Holmes' Facebook Page for more tips for entrepreneurs ;)