Creer and pensar can sometimes be used interchangeably, but not usually. Matching them up with English to believe and to think is not a good idea either. Trying to list the basic connotations of each, I'd say that it's like this:
- belief or conviction
- subjective judgement
- quick assessment
- (objectively) reported state of thoughts
- informed opinion
- possible plan
The verbs might overlap when used to report an assessment on some objective fact, e. g. someone else's work:
- Creo que ella trabaja muy bien.
- Pienso que ella trabaja muy bien.
To me these are roughly equivalent but creo que… shows it's just my opinion, while pienso que… somehow tells the hearer that I've given thought to the matter (maybe because I've been prompted to do so). Alternatively, creo que… could just be used to soften an otherwise direct (and possibly uncalled-for) assertion.
As for your example,
Creo que perderemos el tren si no nos apuramos.
Here creo que… is most natural, while pienso que… would sound a bit forced. As above, creer connotes subjective judgement (in this case, a rough, quick assessment of time). Pensar would more appropriate for another context; for example, you could be sitting with your friends checking railroad timetables, and after a while you could say:
Pienso que sería mejor salir temprano para alcanzar el tren de las 7:45.
Mind you, you could also say creo que… in the example above; it's only that pienso que… tells your hearers you've actually been thinking about it.