Don’t have time
Too tired
Don’t like exercise  
It’s boring
It’s too crowded
It’s too late
It’s too early
It’s too cold
It’s too hot
I’ll get started next week
It hurts too much
I have to lose weight first
I’m too old
I don’t get results
I’ll get big muscles
I have to get in shape first
I don’t know how
It’s raining/it’s snowing
I don’t have a partner
I’m too stressed
I’m too depressed
It’s a waste of time
I can’t afford it
I’m too busy

Don’t let excuses sabotage your plans.